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Feb 2018 Southwest Climate Outlook - La Niña Events in the Southwest

Monday, February 19, 2018

Winter precipitation (Dec-Feb (DJF)), during most weak La Niña events (ENSO Index Value between -0.5 and -1.0) has been below average, although a few years (1968, 1985) were notable outliers (Figs. 5-6). The monthly breakdown of weak, moderate, and strong La Niña events reveals that while the DJF totals for Tucson, AZ and Las Cruces, NM have been mostly below average (Figs. 7-8), there have been individual months that recorded precipitation above the monthly average (represented by black lines on the plots). The most likely outcome for the Southwest this year is below-average precipitation totals for the winter season, but the way that these events unfold will have an impact on how residents perceive and experience this La Niña event (see the following page for examples from Arizona and New Mexico during La Niña events).

Recent La Niña Events - Winter Temperature & Precipitation (Dec 1 - Feb 14)

Temperature anomalies (show below as departures from normal) have been mostly warmer than average during the core of this winter season (Dec 1-Feb 14) across the Southwest (Fig 9). The accumulation plots in Figure 10 display the average precipitation for this timeframe (blue), the observed precipitation this year (green), and the observed precipitation for two recent La Niña events (red, purple) (Fig. 10). These plots reveal similar accumulation patterns, especially in the southern locations, and highlight just how far behind the normal accumulation we are in most of the Southwest.

Feb 2018 Southwest Climate Outlook - La Niña Tracker

Friday, February 16, 2018

La Niña conditions continued for another month, with both atmospheric and oceanic conditions demonstrating a La Niña pattern (Figs. 1-2). Forecasts continue to suggest a weak-to-moderate La Niña event that has likely peaked and will gradually weaken this spring. On Jan. 30, the Australian Bureau of Meteorology saw evidence in recent observations that the event has peaked and is likely already in decline. On Feb. 8, the NOAA Climate Prediction Center (CPC) continued its La Niña advisory based on oceanic and atmospheric conditions, but identified a 55-percent chance of a transition to ENSO-neutral in the spring. On Feb. 8, the International Research Institute (IRI) issued its ENSO Quick Look calling for La Niña to last into the spring (Fig. 3) as a weak-to-moderate event, with a likely return to neutral conditions by mid-spring. On Feb. 9, the Japanese Meteorological Agency (JMA) identified ongoing La Niña conditions straddling weak to moderate strengths and called for a 70-percent chance that the event will end this spring. The North American Multi-Model Ensemble (NMME) is consistently indicative of a weak La Niña event returning to neutral conditions by spring (Fig. 4).

 

Summary: This La Niña event has hovered in the weak-to-moderate range, although it appears to have finally reached moderate strength at the time of this writing. La Niña strength matters in the Southwest, but intensity is not the only factor that affects winter temperature and precipitation patterns. Warmer- and drier-than average winter conditions are associated with La Nina events of any strength, so the presence of La Nina is certain to heighten concerns about winter precipitation and drought, regardless of strength. At the same time, Southwest winters are relatively dry to begin with, so the existence of La Nina does not necessarily bring winter conditions that depart radically from normal, even as they are reliably not wetter than average. However even ENSO-neutral winters have included some of driest (as well as wettest) winters on record. One notable linkage when looking at past events is La Niña conditions generally take wetter-than-average winters off the table. The recent winter storms in the Southwest represent a welcome change, but given the conditions observed so far this winter, a warmer- and drier-than-normal winter certainly appears to be the most likely trajectory.


Online Resources

  • Figure 1 -Australian Bureau of Meteorology - bom.gov.au/climate/enso
  • Figure 2 - NOAA - Climate Prediction Center - cpc.ncep.noaa.gov
  • Figure 3 - International Research Institute for Climate and Society - iri.columbia.edu
  • Figure 4 - NOAA - Climate Prediction Center - cpc.ncep.noaa.gov

SW Climate Outlook - La Niña Tracker - Dec 2017

Friday, December 22, 2017

After a relatively late start, La Niña has ramped up over the past 30 days in terms of observed conditions and projected intensity, with sea-surface temperatures (SSTs) demonstrating a more consistent La Niña pattern (Figs. 1-2). Current forecasts and outlooks suggest a weak-to-moderate La Niña event lasting through the winter. On Dec. 11, the Japanese Meteorological Agency (JMA) identified ongoing La Niña conditions and called for a 60-percent chance of these conditions persisting until spring 2018. On Dec. 14, the NOAA Climate Prediction Center (CPC) extended its La Niña advisory, identifying an 80-percent chance of La Niña conditions lasting through the winter, with a likely transition to ENSO-neutral in the spring. The CPC forecast consensus identified La Niña conditions in the sea-surface and sub-surface temperatures as well as in atmospheric patterns. On Dec. 19, the Australian Bureau of Meteorology updated its ENSO tracker to reflect the emergence of La Niña conditions, but noted that this event was “expected to be short-lived.” On Dec. 19, the International Research Institute (IRI) issued its December ENSO quick look, calling for La Niña to last into the spring (Fig. 3), most likely as a weak event, but with the possibility of increasing to moderate strength. The North American Multi-Model Ensemble (NMME) is consistently indicative of a La Niña event of weak to moderate intensity this winter (Fig. 4). 

Summary: The seasonal outlooks converged on a forecast for La Niña to last through the winter based on consistent La Niña patterns observed in both oceanic and atmospheric indicators. The intensity of the event is still under consideration, with a weak event the most likely scenario, but with increasing possibility of a moderate event mainly due to models and forecasts nudging towards the moderate threshold in the past month. Given the warmer- and drier-than-average winter conditions associated with La Niña in the Southwest, its presence may heighten ongoing concerns regarding winter precipitation and persistent drought. Southwestern winters are already relatively dry, however, so the emergence of a La Niña doesn’t necessarily ensure an exceptionally dry winter, it just takes wetter-than-average winters off the table based on past La Niña events. If the La Niña strengthens to moderate intensity, the likelihood of an even drier Southwest winter increases (see following page for a few examples).


Online Resources / Image Credits

Green Infrastructure as a Climate Action Planning Strategy for the Southwest

Tuesday, November 28, 2017

Climate Change

The climate of southern Arizona is characterized by a few notable extremes, excess heat and lack of water. For the Pima County in the State of Arizona, average mean temperatures have been steadily increasing for the past 30 years. 

Figure 1: West Wide Drought Tracker, created: 10-31-2017


Warm temperatures are one of the region’s most defining characteristics.  According to the Western Regional Climate Center, in Arizona "high temperatures are common throughout the summer at the lower elevations and temperatures over 125 degrees F have been observed in the past”. The southwest region also records relatively low annual precipitation totals, averaging less than 12 inches of rainfall in the past year.

Figure 2: PRISM Climate Group, Oregon State University


A large percentage of precipitation that does fall occurs as intense rainfall during the monsoon (Jun 15 – Sept 30).  Current projections for the future climate of the Southwest including forecasts of gradually warming temperatures, more frequent and intense heat wave events, and increased uncertainty about precipitation along with increased incidence of drought. 

Figure 3: Assessment of Climate Change in the Southwest United States


Population growth and competition over water resources places increasing demands on existing water supplies, which are subject to demand from end-users and fluctuating levels related to temperature and precipitation patterns. In order for the Southwest to increase its capacity to respond effectively to future changes in climate, the region must begin to integrate innovative solutions that support sustainable development. 

Figure 4: Assessment of Climate Change in the Southwest United States


Climate Adaptation Strategies: Green Infrastructure

Sustainable development has grown in popularity as cities in the southwest are increasingly looking for new strategies to assess and respond to the anticipated future climate and environmental changes.  Preliminary approaches for implementing sustainable development first begin with understanding the regions’ climate; there first needs to be a clear understanding of what is causing the problem in order to move forward and address the larger issues. For the Southwest, an issue that has become a priority concern is the increased frequency of drought from warming temperatures due to climate change, and how that will impact the supply of water in the near future. In order to conserve water, communities in arid and semi-arid climates are increasingly recognizing green infrastructure as a cost-effective approach that conserves water and also manages stormwater.6

Green infrastructure refers to a set of practices that mimic natural processes to retain and use stormwater. By promoting infiltration, evapotranspiration, and harvesting throughout the landscape, green infrastructure preserves and in some cases restores natural water balance.6  Commonly referred to as a Low impact Development (LID), the system consists of soils and vegetation that are used to manage stormwater through mimicking natural flow of water and use it for multiple benefits for both the environment and community. The United States Environmental Protection Agency (EPA) has a list of different G.I. elements that can be woven into a community, ranging from small scale to large scale elements spanning entire watersheds. Strategies that are commonly seen in metropolitan regions such as Tucson include rainwater harvesting collection systems (cisterns), rain gardens (also known as bioretention and bioinfiltration), bioswales and green streets (combination of street curb cuts and bioswales) (See . 

Image 1 (above): Original Street Curb Cut, source: Harvesting Rain Water. Multi-use rain-garden plant lists: Invitations to Deeper and More-connected relationships

Image 2 (below): Street Curb Cut After Improvements, source: Harvesting Rain Water. Multi-use rain-garden plant lists: Invitations to Deeper and More-connected relationships. 


When implemented properly, green infrastructure has the potential to create more resilient communities and further strengthen their ability to respond to climate vulnerability. In order to be effective however, a city’s green infrastructure initiative must incorporate different guiding principles, one of which includes place-based approaches. Place-based projects are site-specific and community based. Implementation of such projects incorporates the community with stakeholders and these dual partnerships engage to ensure the planning process recognizes distinctions within a city across ecological, social and cultural dimensions.1 

City-led Initiatives and Non-profit collaborations

The Southwest has a great capacity to respond to these alarming environmental stresses and to lead in ensuring stewardship with natural resources. One city within the Southwest that has already implemented place-based approaches regarding green infrastructure projects is Tucson. Tucson has established the Framework for Advancing Sustainability program where its intent is to create a decision-making framework that explicitly considers sustainability and facilitates sustainable development within the community. Under this framework, specific goals have been designed to address climate adaptation, which include the following:

  • Encourage public and private action in support of resilient social and economic systems that can withstand the stress induced by anticipated climate change impacts within the region
  • Provide outreach and education to the community to enable individuals and groups to take action to improve the sustainability of Tucson

A non-profit organization that is leading in implementing these goals is the Watershed Management Group. Watershed Management Group (WMG) is a Tucson based organization that has developed community based solutions that ensure long-term prosperity of people and the health of the environment. Most of the projects they develop include the ability to provide people with the knowledge, skills, tools, and resources needed to create sustainable livelihoods. They have identified the value in stormwater management through landscape design and have further implemented green infrastructure projects throughout the city of Tucson to conserve water and mitigate flooding while at the same time, educating the public realm. Their most notable work includes their Green living Co-op, their Green Streets Program, their Advocacy and Public Policy through the Community Water Coalition, and their 50 Year Program to restore Tucson’s free flowing rivers.

WMG’s work has led to direct impacts on the Tucson community. Their Green Streets Program builds partnerships with different companies, non-profits, neighborhoods and municipalities and encourages collaboration efforts between them to install green streets. Green streets help conserve water, reduce urban flooding and stormwater pollution while at the same time, lessening the urban heat island effect. In short, G.I. presents an opportunity for communities to partner with non-profits to make a significant impact in response to climate change. G.I. has a direct impact on climate change.

Direct impacts is seen in one of WMG’s large-scale projects, whom they partnered with the Pima County Regional Flood Control District (PCRFCD) to solve the flooding challenges faced by residents in an area south of the Airport Wash.  G.I. retention capacities were assessed using 2-dimensional hydrological models for three different watersheds. Results showed that by implementing G.I. throughout the watersheds in a 25-year scenario would lead to $2.5 million dollars of annual community benefits as a result from of flood reductions, water conservation, property value increase, reduced urban heat island impacts.9 A cost benefit analysis was also included to assess the full range of benefits throughout the area south of the Airport wash.

Four main practices were evaluated for the cost benefit analysis (CBA): rain gardens, rain gardens with curb cuts, rain garden retrofits and green street water harvesting features. The benefits for the CBA were based on the inputs of the number and average size of trees planted, area of water-harvesting basins, and volume of water-harvesting basins. A graph of a 35-year projection of a rain garden cost and direct benefit showed conclusive results. For a 100 square foot rain garden, although the cost in the first year was over $600, by the end of 5 years, direct benefits would outweigh the costs significantly. After 10 years, revenue would increase exponentially. 

Figure 5: Watershed Management Group pdf. 


Future considerations

Different parts of the Southwest are experiencing drier and hotter conditions, much of which is attributable to climate change. As severe drought events are further depleting the current water supply, cities will find compelling reasons to explore alternatives to meet water demands7. In order to meet the needs of current water supply and demand, climate resilient strategies will be vital for the near future projections.  One climate resiliency strategy that has shown tremendous benefits is G.I. G.I. describes an approach to managing stormwater, where vegetation is used to capture water and through the process of infiltration, water is stored below ground surfaces and later reused. In our current built environment, many homeowners use drinking water to irrigate their lawns. By implementing rain water catchment systems, potable water usage is ultimately reduced, which consequently leads to lowering the stress on the demand for water supply.  Other benefits from G.I. practices include the ability to create greater air movement, reflection of heat, and provide shading that can cool urban environments.

Although stormwater management through green infrastructure may have many benefits within different climatic regions, there still exists overseen setbacks and barriers. One of the biggest barrier is the lack of funding. At least at the federal level, there is no single source of dedicated federal funding to design and implement green infrastructure solutions. Without assistance, communities take several approaches to financing wastewater and stormwater projects through the use of municipal bonds10, which may not always be the best alternative. However, there are a few helpful resources, such as the EPA’s financing options and resources for local decision-makers report, that discuss both pros and cons for several sources of funding for small-scale projects.  Other barriers include the lack of information on performance overtime and cost-effectiveness, the uncertainty of water quality improvement and the maintenance required to maintain these systems over time.


References

  1. Brown, Hannah J. (2017). Green Infrastructure: Best Practices for cities. U.S. Green Building Council. Advocacy and Policy section.
  2. Pagnet.org. (2017). Green Infrastructure. (online) Available at: https://www.pagnet.org/Default.aspx?tabid=189. Accessed 19 Nov. 2017.
  3. AdaptationClearinghouse (2008). City of Tucson, Arizona Framework for Advancing Sustainability. (online) Available at: http://www.adaptationclearinghouse.org/resources/city-of-tucson-arizona-.... Accessed 19 Nov. 2017.
  4. MacAdam, James, T. Syracuse, J. DeRoussel, and K. Roach.  (2012). Green Infrastructure for Southwestern Neighborhoods. Watershed Management Group.pdf.
  5. Garfin, G., A. Jardine, R. Merideth, M. Black, and S. LeRoy, eds. (2013). Assessment of Climate Change in the Southwest United States: A Report Prepared for the National Climate Assessment. A report by the Southwest Climate Alliance. Washington, DC: Island Press.
  6. Liverman, D., S. C. Moser, P. S. Weiland, L. Dilling, M. T. Boykoff, H. E. Brown, E. S. Gordon, C. Greene, E. Holthaus, D. A. Niemeier, S. Pincetl, W. J. Steenburgh, and V. C. Tidwell. (2013). “Climate Choices for a Sustainable Southwest.” In Assessment of Climate Change in the Southwest United States: A Report Prepared for the National Climate Assessment, edited by G. Garfin, A. Jardine, R. Merideth, M. Black, and S. LeRoy, 405–435. A report by the Southwest Climate Alliance. Washington, DC: Island Press.
  7. Green Infrastructure in Arid and Semi-Arid Climates: Adapting innovative stormwater management techniques to the water-limited West. (2009). Retrieved from https://www3.epa.gov/npdes/pubs/arid_climates_casestudy.pdf
  8. Lancaster, B., J. MacAdam, J. Miller, K. Roach, C. Shipek, L. Shipek, J. Silins, S. Somnath, T. Syracuse. (2011). The Ripple Effect Annual Report.  Watershed Managent Group.
  9. (2015). Solving Flooding Challenges with Green Stormwater Infrastructures in the Airport Wash Area. Watershed Management Group in collaboration with Pima County Regional Flood Control District. Pdf.
  10. Copeland, Claudia. (2016). Green Infrastructure and Issues in Managing Urban Stormwater. Congressional Research Service

SW Climate Outlook - ENSO Tracker - Aug 2017

Sunday, August 20, 2017

Oceanic and atmospheric indicators remain within the range of neutral (Figs. 1-2). Seasonal outlooks and forecasts generally agree that ENSO-neutral conditions are the most likely outcome through winter 2017-2018. On Aug. 10, the Japanese Meteorological Agency (JMA) identified a continuation of ENSO-neutral conditions with a 60-percent chance of El Niño conditions until winter 2017-2018. On Aug. 10, the NOAA Climate Prediction Center (CPC) observed that oceanic and atmospheric conditions remained within the range of ENSO-neutral conditions, and that “the majority of models favor ENSO-neutral for the remainder of 2017.” They identified an 85-percent chance of neutral conditions through September 2017, and a 55-percent chance through February 2018. On Aug. 15, the Australian Bureau of Meteorology ENSO tracker remained at neutral/inactive, highlighting that every indication (models and forecasts) suggested ENSO-neutral conditions through 2017. On July 20, the International Research Institute for Climate and Society (IRI) and CPC identified a high likelihood of ENSO neutral conditions for the rest of 2017 (Fig. 3). The North American Multi-Model Ensemble (NMME) is ENSO-neutral as of August 2017. The model spread indicates a range of outcomes for the rest of 2017 (Fig. 4), but the ensemble mean indicates ENSO-neutral as the most likely outcome.

Summary: As with last month, ENSO indicators remain well within the bounds of ENSO-neutral, and there is little to suggest any other outcome in winter 2017-2018. An interesting detail has emerged from a few of the forecast discussions, however: the appearance of a slight uptick in the likelihood of a La Niña event in 2017-2018, running counter to discussion of the last few months. What’s going on? In Fig. 3, subtracting the current forecast percentage (bars) from the seasonal climatological probability percentage (lines) flattens the plot and reveals the deviation from normal climatology these forecast percentages represent (Fig. 5). Under this formulation, neutral conditions are forecast well above their climatological average through winter 2017-2018, while both El Niño and La Niña conditions are below their climatological average. This corresponds with current forecasts discussed above, and given the expected uncertainty associated with longer-term forecasts, the forecast percentages converge on climatological averages by the Mar-Apr-May period of 2018.


Online Resources

SW Climate Outlook - Monsoon Tracker - July 2017

Monday, July 24, 2017

The official start date of the monsoon (June 15) was overshadowed by a Southwest-wide extreme heatwave that set numerous records. Heatwaves in June are a typical feature of the seasonal climate, especially as the subtropical ridge builds north, but these record temperatures also increased the anticipation for the relief that the monsoon can provide. Much of southern and central Arizona have recorded pockets of above-average precipitation, while New Mexico has seen more widely distributed precipitation since June 15 (Fig. 1a-b). The maps highlight the extreme spatial variability of monsoon precipitation and the difficulty of scoring or grading the monsoon performance using single stations or summary maps (not that we don’t continue to try!). Another useful metric is the percent of days with rain, which, when used with the precipitation maps, distinguishes areas that have received more frequent and moderate precipitation from those in which just a few extreme events boosted seasonal totals. In Arizona, the southeastern corner and a swath across the higher-elevation areas of the central part of the state have received the most consistent precipitation, with significant variability across other areas (Fig. 2a). In contrast, precipitation frequency is relatively uniform across most of New Mexico, reflecting an earlier start to the monsoon as well as more overall precipitation activity (Fig. 2b).

CLIMAS SW Monsoon Outlook - June 2017

Friday, June 16, 2017

In 2008, the National Weather Service changed the definition of the start of the Southwest monsoon from a variable date based on locally measured conditions to a fixed date of June 15. Prior to 2008, the start date reflected the seasonal progression of the monsoon (Fig. 1). This is based on larger seasonal atmospheric patterns and the establishment of the ‘monsoon ridge’ in the Southwest (Figs. 3a-b, also see sidebar for link to NWS pages).

In Southern Arizona, the start date was based on the average daily dewpoint temperature. Phoenix and Tucson NWS offices used the criteria of three consecutive days of daily average dewpoint temperature above a threshold (55 degrees in Phoenix, 54 degrees in Tucson) to define the start date of the monsoon. As shown in Figure 2, the dewpoint temperature criterion produced start dates ranging from mid-June to late July over the period of record (1949-2016). The average daily dewpoint temperature is still a useful tool to track the onset and progression of conditions that favor monsoon events, and the National Weather Service includes a dewpoint tracker in their suite of monsoon tools.

Thirty-year averages for daily dewpoint and precipitation demonstrate the gradual increase in dewpoint temperatures during the monsoon season, as well as the variability of precipitation observed over the same window (Fig. 4).

The updated definition of the monsoon identifies a season that lasts for 108 days with defined start and end dates of June 15 and Sept 30. In the Southwest, however, the majority of monsoon storm activity occurs in July and August (Fig. 5), with some lingering activity into September (occasionally augmented by eastern Pacific tropical storms). Dewpoint and precipitation may provide a more granular assessment of monsoon activity, but the seasonal designation allows for easier comparisons between years, and focuses planning activities on a discrete monsoon season (see NWS video about Monsoon Awareness Week).


Online Resources:

CLIMAS SW Climate Outlook - ENSO Tracker June 2017

Friday, June 16, 2017

Oceanic and atmospheric indicators of the El Niño-Southern Oscillation (ENSO) are still within the range of neutral (Figs. 1-2), although sea-surface temperatures more consistently hint at borderline El Niño conditions compared to atmospheric indicators. Outlooks and forecasts generally agree that ENSO-neutral conditions will persist through the summer and is the most likely scenario for the rest of 2017. A lingering possibility remains of an El Nino event developing later this fall, but forecasts since last month have shifted further from that likelihood.

On June 6, the Australian Bureau of Meteorology maintained its El Niño Watch with a 50-percent chance of an El Niño event in 2017, but noted indicators have remained mostly unchanged for multiple weeks, “suggesting El Niño development has stalled for now.” On June 8, the NOAA Climate Prediction Center (CPC) observed that oceanic and atmospheric conditions were consistent with ENSO-neutral conditions, but recent model runs led CPC forecasters to shift to a 50-55-percent chance of ENSO-neutral conditions in 2017 and a 35-50 percent chance of El Niño. On June 9, the Japanese Meteorological Agency (JMA) identified a continuation of ENSO-neutral conditions with a 70-percent chance of El Niño conditions until fall 2017, noting that oceanic and atmospheric conditions “indicate no clear signs of El Niño development.” On June 15, the International Research Institute for Climate and Society (IRI) and CPC identified ENSO-neutral as the most likely outcome in 2017, with a 40-to-45-percent chance of an El Niño in 2017 (Fig. 3). The North American Multi-Model Ensemble (NMME) is borderline weak El Niño as of June 2017, and while the model spread indicates a wide range of possible outcomes for the rest of 2017 (Fig. 4), the ensemble mean indicates ENSO-neutral as the most likely outcome (but with a weak El Niño event still within the range of plausibility), which is reflected in the uncertainty in the CPC and IRI/CPC outlooks.

Summary: The lack of atmospheric indicators of El Niño and the borderline status of sea-surface temperature anomalies have strengthened the forecaster consensus that ENSO-neutral is the most likely scenario for the remainder of 2017. It is too early to entirely rule out an El Niño event later this year, but the timing and intensity of this plausible but increasingly unlikely El Niño event is still relatively uncertain. There are two key takeaways from the current outlooks and forecasts. One, there is a near-zero probability of a La Niña event in 2017. Given that the Southwest shifts toward warmer and drier winter conditions in La Niña years, this is a welcome alternative. Two, given the relatively weak correlation between cool-season precipitation and weak El Niño events, whether ENSO-neutral or weak El Niño conditions ultimately prevail, the overall seasonal outlook for the Southwest would look relatively similar.


Online Resources: 

CLIMAS SW Climate Outlook - Wildfire Report: Sawmill Fire

Friday, May 19, 2017

The Sawmill fire (Fig. 1) started, reportedly by recreational shooting, on April 23, 2017 in a grass- and shrub-covered area of low-elevation Arizona state lands approximately 40 miles south of Tucson. The fire spread quickly due to dry and windy conditions that day: the temperature reached 98 degrees, relative humidity ranged between 4 and 18 percent, and sustained winds reached 20 mph with gusts up to 30 mph. High winds, high temperatures, and low relative humidity continued through much of the following week, driving rapid growth of the fire (Fig. 2).

The strong winds whipped the fire along, challenging ground-level fire-line containment efforts and repeatedly grounding aerial support. Numerous communities and rural households were evacuated, and wildfire management was eventually escalated to a type 1 incident management team. At peak effort, nearly 800 firefighters and multiple aerial tankers were deployed to fight the fire, slow the spread, and protect communities and structures. Initial estimates of the fire put the total acreage burned at 46,991 acres, making it the 14th largest wildfire in Arizona history (Fig. 3).

In the Southwest, peak seasonal wildfire danger varies across the region, ranging from early-mid-May to early June in eastern New Mexico, to late June in western Arizona (Fig. 4). This roughly corresponds to the progression of the monsoon, which brings some relief to the hot and dry conditions that characterize late spring and early-to-mid summer, although dry lightning associated with early monsoon storms sometimes serves as an ignition source for wildfire. June and early July are characterized by the warmest and driest conditions, reaching the peak of the warm-up and dry-out period of late spring into summer.

While fire is possible during most of the year, most wildfire activity clusters in this warm/dry summer period (Fig. 5). The Sawmill fire demonstrates that large fires are possible outside of the peak of summer wildfire season, and was likely the culmination of a set of circumstances that brought about enhanced wildfire risk earlier than is typical in Arizona.

In September 2016, a surge in precipitation associated with hurricane Newton and lingering monsoon activity brought moisture into the Southwest, in particular to the southeastern corner of Arizona where the Sawmill fire broke out (Fig. 6). The rains boosted plant growth and green-up, and by mid-October, above-normal green-up was visible in satellite imagery of the grasslands in the region (Fig. 7). 

Following this explosion of new vegetation, the region experienced an extended drier-than-average period, with water-year precipitation totals for the seven-month period of Oct 2016 to April 2017 well-below average in southern Arizona. (Fig. 8).

Temperatures during the same period were warmer than average across the Southwest, and in some locations approached or set records (Fig. 9). The relative wintertime warmth augmented by early January precipitation further enhanced plant growth. These moderate winter conditions extended the growing season and likely contributed to an early start for spring plant growth and development (for more details see the story about early arrival of spring conditions in 2017, links to a changing climate, and the National Phenology Network).

By late winter, however, heat and lack of precipitation (Fig. 10) had dried out the lower-elevation soils and the new vegetation began to dry out and die. By early-to-mid April, abundant fine fuels had accumulated. Add in strong winds and low relative humidity, and the stage was set for an earlier-than-normal significant wildfire event – all it needed was an ignition source. Although that source was a human, the fire itself, by virtue of its fast-moving nature, did not have severe adverse impacts to the soil and may ultimately be viewed as beneficial to the grasslands.


Image Credits

SWCO ENSO Tracker - April 2017

Friday, April 21, 2017

Similar to last month, oceanic and atmospheric indicators of the El Niño-Southern Oscillation (ENSO) are in the range of neutral (Figs. 1-2), and these conditions are forecast to last through the spring and summer. Most forecasts and outlooks indicate that El Niño conditions could return in mid-to-late 2017, but these assessments come with the annual caveat of increased uncertainty associated with the “spring predictability barrier”, during which time the specifics regarding the possibility, timing, and intensity of an El Niño event are elusive. At any rate, the models and forecasts indicate a near-zero probability of La Niña in 2017, leaving forecasters to decide between the probability of neutral or El Niño conditions in later 2017.

The various forecasts provide insight into the range of predictions for the remainder of spring and the ENSO signal for the rest of 2017. On April 10, the Japanese Meteorological Agency (JMA) identified a continuation of ENSO-neutral conditions, with a 50-percent chance of El Niño conditions by the end of summer, but flagged high uncertainties in the models. On April 11, the Australian Bureau of Meteorology maintained their El Niño Watch, also with a 50-percent chance of an El Niño event. They identified warming oceanic conditions as indicating an increased chance of El Niño conditions in 2017 (and having contributed to recent severe flooding in South America). On April 13, the NOAA Climate Prediction Center (CPC) observed that oceanic and atmospheric conditions were consistent with ENSO-neutral conditions, but that some flagging La Niña-like convection was still affecting their assessment. They forecast a 60- to 65-percent chance of ENSO-neutral conditions for April-June 2017, and a 50-percent chance of El Niño conditions between August and December. On April 20, the International Research Institute for Climate and Society (IRI) and CPC identified ongoing neutral conditions, but with some westerly anomalies that may indicate the “first sign of a brewing El Niño.” The IRI model spread shows a wide range from neutral to strong El Niño, and the mid-April forecast shows an approximately 65-percent chance of an El Niño event starting in summer and lasting through 2017 (Fig. 3). The North American Multi-Model Ensemble (NMME) characterizes the current model spread and highlights the variability looking forward. The NMME mean is projected to reach weak El Niño status by early summer (Fig. 4).

 

Summary: Given the uncertainty associated with springtime forecasts and the waning influence of remnant La Niña conditions, the Southwest remains in a holding pattern regarding an El Niño event in 2017. Even if an El Niño event develops, there is no certainty about the strength of the event or the scale of the impacts likely to be felt in the Southwest.

SWCO: Temperature meets April 2017 Streamflow Forecasts

Friday, April 21, 2017

March 2017 turned out to be the warmest non-El Niño March on record and the second warmest March overall (Figs. 5a-c).

 

The warm temperatures in 2017, in conjunction with mostly above-average precipitation across the West, mean streamflow forecasts remain well-above average (Fig. 6), and ahead of schedule.

SWCO Aug 2016 - La Niña Tracker

Friday, August 19, 2016

Oceanic and atmospheric indicators of the El Niño-Southern Oscillation (ENSO) remain in the range of neutral conditions (Figs. 1-2). Seasonal forecasts and models identify the most likely scenario being a weak La Niña event forming sometime in late summer or fall 2016 and lasting through winter 2017. Some uncertainty exists regarding the specific timing of this event, as the equatorial sea surface temperature (SST) anomalies have not yet dropped into La Niña range and there is a lack of coordination between ocean and atmosphere (and in particular the lack of enhanced trade winds).

A closer look at the various forecasts and seasonal outlooks provides insight into the range of expectations for this La Niña event. On August 10, the Japanese Meteorological Agency saw below-normal equatorial convective activity and enhanced trade winds as indicative of the start of La Niña-favorable conditions, even while the SST anomalies were slow to swing more negative (cool) after the sustained warm period associated with El Niño conditions. The agency forecast a 70 percent chance of a La Niña event developing, but not until fall 2016. On August 11, the NOAA Climate Prediction Center (CPC) highlighted ENSO-neutral conditions in both ocean and atmosphere and continued to focus on tension between statistical and dynamical models, the former predicting a later onset and weaker event than the latter. The CPC forecast remains at a 55–60 percent chance of a weak La Niña event starting sometime between August and October 2016. On August 16, the Australian Bureau of Meteorology maintained its La Niña watch, albeit with slightly reduced confidence compared to the previous month, hedging slightly by stating “if La Niña does develop it is likely be weak.” The bureau maintained its forecast probability at a 50 percent chance of a La Niña event developing, noting that is approximately twice the normal chance of a La Niña forming. On August 18, the International Research Institute for Climate and Society (IRI) and CPC forecasts indicated the probability of a “borderline/weak” La Niña forming was just less than 60 percent (Fig. 3). The IRI forecasters noted that until the atmosphere cooperates (i.e., the enhanced trade winds show up), the ENSO-neutral holding pattern will remain. The North American multi-model ensemble characterizes the current model spread and highlights the variability looking forward to 2017, but the ensemble mean hovers close to weak La Niña status for fall and winter of the coming year (Fig. 4).

The Southwest is in a holding pattern regarding La Niña but will likely see the effects of a weak La Niña this winter. Forecasters are likely already integrating the influence of the drier-than-average signal associated with La Niña into long-term precipitation and temperature forecasts and seasonal outlooks (Fig. 5a-b), and researchers are preparing to track both the timing and intensity of this event in relation to precipitation, temperature, snowpack, and water supply over the coming year. 

Given the dry climate of the Southwest, a weak La Niña event does not necessarily deviate far from the seasonal climatology of the region, but while ENSO-neutral winters have a wider range of precipitation values observed over winter, La Niña winters skew more dry. Even a weak La Niña event is likely to suppress winter precipitation totals in the Southwest, which is unwelcome news given the underperformance of last year’s El Niño winter and the longer-term effects of multi-year drought.

SWCO Aug 2016 - Monsoon Tracker

Friday, August 19, 2016

The Southwest saw the first strong burst of widespread monsoon activity near the end of June.  Most of the first half of July was characterized by a distinct break in monsoon activity, as atmospheric circulation patterns and lack of available moisture limited opportunities for widespread storms to develop, especially at lower elevations.  As July progressed, there were increasingly favorable conditions for storms to develop and spread, culminating in an extended period of widespread activity during late July and early August. Tropical Storm Javier helped jumpstart activity in mid-August, just as the previously mentioned extended run was winding down, and provided a brief extension to storm activity via a surge of moisture from the Gulf of California. The remainder of the monsoon window will be a waiting game to see if favorable moisture and atmospheric circulation patterns develop, as well as the potential influence of eastern Pacific tropical storm activity that could supplement storm activity and provide additional moisture to fuel storm activity.

Based on cumulative totals since the official start of the monsoon, most of Arizona recorded average to below-average precipitation, even while clusters of the state have recorded above-average precipitation as a percent of average (Fig. 2a) and in terms of outright totals (Fig. 3a). The percent of days with rain highlights the spatial variability of the monsoon and emphasizes the clustering of storms in the southeastern corner of the state (Fig. 4a). Precipitation plots from specific stations further highlight this variability, with Douglas, Flagstaff, and Tucson stations all on pace for average to above-average monsoon totals (Figs. 5a-c) but with the Tacna station in the southwest corner of Arizona yet to record a precipitation event (Fig 5d).

Cumulative totals since the start of the monsoon show that much of New Mexico recorded average to below-average precipitation, but with wider areas of above-average rainfall as well (Figs. 2b – 3b). The percent of days with rain also highlights the more regular coverage seen in New Mexico, with a wider swath of increased activity that covers most of the state (Fig. 4b). Station plots also demonstrate the lagging precipitation in select locations, with Albuquerque and El Paso, Texas, lagging behind seasonal totals (Figs. 5e-f). Stations closer to southern Arizona, such as the Animas 3ESE station, are recording above-average precipitation (Fig. 5g).

The southwestern monsoon is characterized by a high degree of spatial and temporal variability. Over the course of the season, storm events are interspersed with breaks of limited activity as migrating high pressure systems and available moisture dictates where in the Southwest rain might fall. This results in highly variable precipitation totals on a daily or weekly scale. Regional climatology gives some indication as to the expected cumulative total precipitation any location might expect but says less about how those precipitation totals will be achieved. Any given year of monsoon activity is difficult to categorize on a week-to-week basis, and simple score-carding using seasonal precipitation to date will be skewed by recent runs of heavy rain or extended breaks in the monsoon. Looking at daily precipitation event maps, there are very few days in which no rain fell anywhere in Arizona or New Mexico; there are numerous locations that saw little to no rain while nearby regions saw extensive precipitation.  These totals should generally start to even out over the course of the season and vary around the long-term average, but outliers and extremes are always possible.  As stated above, the remainder of the season is a waiting game to determine if and when a favorable atmospheric circulation brings additional storm activity into the region, or if tropical storm activity can help jumpstart these storms with additional surges of Gulf moisture.

July 2016 SW Climate Outlook - La Niña Tracker

Friday, July 22, 2016

All oceanic and atmospheric indicators of the El Niño-Southern Oscillation (ENSO) have returned to neutral conditions (Figs. 1-2). The development of a La Niña event in 2016 remains a distinct possibility, even while the timing and intensity remain relatively uncertain. 

On July 14, the NOAA Climate Prediction Center (CPC) highlighted the persistent neutral conditions currently observed and identified some tension between statistical and dynamical models, the former predicting a later onset and weaker event than the latter. The CPC forecast took a middle ground between these models and forecast a 55–60 percent chance of a weak La Niña event starting sometime between August and October 2016. On July 19, the Australian Bureau of Meteorology maintained its La Niña watch but saw some recent declines in model projections that decreased the forecast probability to a 50 percent chance of a La Niña event developing. On July 21, the International Research Institute for Climate and Society (IRI) and CPC forecasts highlighted that while most of the oceanic and atmospheric conditions were indicative of a La Niña event forming, the trade winds had not yet shifted towards La Niña, and there was a lack of coupling between ocean and atmosphere that is crucial to the formation of a La Niña event. The IRI-CPC forecast still sees the formation of a La Niña event in 2016 as more likely than not, but with the timing delayed and the intensity of the event not likely to exceed weak status (Fig. 3). The North American multi-model ensemble characterizes the current model spread and highlights the variability looking forward to 2017, but the ensemble mean hovers close to weak La Niña status for fall and winter of the coming year (Fig. 4).

La Niña typically brings drier-than-average conditions to the Southwest, and it will be important to track both the timing and intensity of this event in relation to precipitation, temperature, snowpack, and water supply over the coming year. CLIMAS researchers are contributing to a La Niña information hub that will mirror the El Niño hub, with the goal of providing a curated set of news and forecast models regarding La Niña, as well as expert commentary and analysis on the possible impacts to the Southwest. 

Visit climas.arizona.edu for more information.

July 2016 SW Climate Outlook - Monsoon Tracker

Friday, July 22, 2016

The southwestern monsoon officially starts June 15 and ends September 30 – the dates the National Weather Service began using in 2008 to identify the window of typical activity for the region. The historical start date of monsoon activity (increased dew point, onset of precipitation events) varies across the region and is reflected in a generally westward migration over the season (Fig. 1). The monsoon ridge also shifts throughout the season, and the location of this ridge helps determine where storms and precipitation events will occur. 

The Southwest saw a strong start to the monsoon in the second half of June, with a number of heavy rainfall events, particularly across southern Arizona. Most of July has been characterized by a monsoon “break” for the Southwest, with very few precipitation events other than in the southeastern corner of Arizona. Since the start of the monsoon, most of Arizona and New Mexico have recorded below-average precipitation (Figs. 2a-b), but this is early in the season and a wide range of precipitation totals and considerable spatial variability is to be expected at this point (Figs. 3a-b). The percent of days with rain highlights the irregular coverage of monsoon precipitation thus far, with much of the heavy precipitation activity clustered in southeastern Arizona and across much of New Mexico (Figs. 4a-b).

June 2016 SW Climate Outlook - ENSO Tracker

Friday, June 17, 2016

El Niño conditions continued their active decline (Figs. 1-2), and consensus is that they have reached ENSO-neutral status at the time of this writing. Forecast discussions focused on the decline of atmospheric and oceanic anomalies that characterize an El Niño event—convective activity, equatorial sea surface temperatures, and trade winds—and forecasters saw consistent evidence of a return to ENSO-neutral status across these indicators. Seasonal ENSO outlooks coalesced around La Niña conditions emerging by summer or fall 2016, with relatively high certainty that La Niña conditions would be in place sometime by mid-to-late 2016.

On June 7, the Australian Bureau of Meteorology maintained its outlook at La Niña Watch status, noting that the tropical Pacific Ocean was in an ENSO-neutral state, with a 50 percent probability of a La Niña event developing in 2016. On June 9, the NOAA-Climate Prediction Center (CPC) issued a final El Niño Advisory, while maintaining a La Niña Watch. The CPC identified atmospheric and oceanic anomalies as reflecting ENSO-neutral conditions and forecast La Niña conditions would develop over the summer, with a 75 percent probability of a La Niña during fall and winter 2016-2017. On June 10, the Japan Meteorological Agency identified that El Niño conditions ended in late spring 2016, with an increasing likelihood of La Niña developing over summer and into fall. On June 16, the International Research Institute for Climate and Society (IRI) and CPC forecasts identified ENSO-neutral conditions in oceanic and atmospheric indicators, with La Niña emerging by late July or August and lasting through fall and winter (Fig. 3). The North American multi-model ensemble currently shows the decline from strong El Niño status to neutral conditions, as well as a relatively rapid swing to La Niña conditions by summer (Fig. 4).

As very clearly experienced during the El Niño event of 2015–2016, there is no guarantee that a given event will meet expectations (see El Niño tracker in the May 2016 Southwest Climate Outlook for more details). That said, it is important to note that La Niña events are associated with decreased cool-season precipitation in the Southwest. This is a more reliable pattern in terms of forecasts and predictions, with La Niña events being more reliably dry than El Niño events are reliably wet, and considerable variability between wet and dry in ENSO-neutral years. With a La Niña forecast on the horizon for winter 2016–2017, drier-than-average cool-season precipitation totals are a likely outcome, with implications for long-term drought and water storage concerns in the Southwest.

El Niño Recap & La Niña Outlook - May 2016

Saturday, May 21, 2016

El Niño Recap & La Niña Outlook

This El Niño event was one of the strongest ever recorded (Fig. 5), and if past performance was any indication of what was expected for the Southwest, the region should have seen above-average precipitation over much of the cool season (winter and spring). The Southwest generally saw lower-than-expected precipitation totals that were much closer to average, or even below average in some cases.  There are several reasons why this event did not meet expectations. One explanation is the difficulty of predicting highly variable weather events within the context of climate. In the case of the El Niño event of 2015–2016, a ridge of high pressure diverted moisture away from the Southwest during the prime time we might have expected to see increased activity (see El Niño tracker in April 2016 SWCO for details). Another reason is related to the use of analogs, past strong events, such as the El Niño event in 1982–83 or 1997–98). This El Niño event looks to be a clear outlier compared to most other observations that quantify the relationship between the ENSO index value and precipitation anomalies (Fig. 6). This analysis is hampered by limited sample size, which means making broad pronouncements about these patterns is problematic until there are more observations of strong El Niño events to compare to this event, and more data to feed into seasonal forecasts and outlooks. A final reason for the recent El Niño falling short of expectations is the relative infancy of the science of El Niño. The climate and atmospheric/oceanic science community is still developing its understanding of El Niño and the influence of the Arctic Oscillation Index or the Pacific Decadal Oscillation. Experts in these fields will certainly look to this El Niño event to determine what additional information can be gleaned from an event that, by all accounts, could have blanketed the Southwest with regular and steady winter precipitation. Instead, warm and dry conditions dominated throughout much of the cool season in the Southwest, even while the El Niño event performed closer to expectations across most of the globe (Fig. 7).

Perhaps just as importantly, this discrepancy between seasonal outlooks and forecasts and the observed weather of the cool season did not take place in a vacuum. Long-term drought has affected the Southwest throughout much of the 21st century, and the prospect of a strong El Niño event generated considerable hope and optimism for the potential positive impacts of above-average precipitation. This optimism was augmented by media-fed narratives about the potential for extreme precipitation during a strong El Niño event that did not include the necessary caveats associated with most scientific models and forecasts. Still, it was generally understood that a single strong year would not “fix” long-term drought, but that it might at least bend the curve back towards some modicum of recovery. Near-average cool-season precipitation was disappointing when held up to these expectations but was much wetter than would be expected in a typical La Niña winter, a comparison that will be all the more salient by this time next year.

A strong El Niño event is typically associated with increased precipitation across the cool season in the Southwest, but there is a practical limit to how much additional precipitation a desert environment might experience, even in a record El Niño year. Conversely, a La Niña event is associated with decreased cool-season precipitation in the Southwest, somewhat more reliably in terms of forecasts and predictions; layering a dry signal (i.e., La Niña) onto an already dry climate may produce a more consistent result compared to layering a wet signal (i.e., El Niño) onto a dry climate (Fig. 8). The correlations between ENSO status and precipitation anomalies do generally follow this pattern; La Niña events are more reliably dry than El Niño events are reliably wet, and there is considerable variability between wet and dry in ENSO-neutral years. The El Niño event of 2015–2016 was decidedly average and a likely outlier from previous (and subsequent) El Niño events. The La Niña conditions forecast for 2016–2017 are much more likely to produce drier-than-average cool season precipitation totals, with implications for long-term drought in the Southwest.

El Niño Tracker - March 2016 - Time Winding Down for El Niño in the Southwest

Friday, March 18, 2016

Originally published in the Mar 2016 CLIMAS Southwest Climate Outlook

El Niño conditions continued for a 13th straight month, but the peak of this event has passed. Monitoring and forecast discussions emphasize strong positive sea surface temperature (SST) anomalies (Figs. 1–2) and enhanced convective activity in the central and eastern Pacific. These positive temperature anomalies are waning, and trade wind activity is increasing, indications that this El Niño event is on the decline. Most forecasts emphasize this event will continue through spring or early summer before returning to ENSO-neutral status. There is also the possibility of swinging to La Niña conditions later in 2016, although there is considerable model and forecast uncertainty regarding the chances of La Niña vs. ENSO-neutral conditions.

On Mar. 10, the Japan Meteorological Agency identified ongoing El Niño conditions that had peaked and were actively decaying and expected to weaken to neutral conditions by summer.  On the same day, the NOAA-Climate Prediction Center (CPC) extended its El Niño advisory, identifying current atmospheric and oceanic anomalies as reflecting a strong El Niño that will likely persist through most of the spring before transitioning to ENSO-neutral conditions in late spring or early summer. On Mar. 15, the Australian Bureau of Meteorology maintained its tracker at official El Niño status, but noted a slow and steady decline, with decreasing positive temperature anomalies and near-normal trade winds as two key indicators of this event’s ongoing deterioration. On Mar. 17, the International Research Institute for Climate and Society (IRI) and CPC forecasts described mixed signals regarding El Niño, with zonal winds and SSTs in decline, while convective activity and the Southern Oscillation Index (SOI) remained strong. The IRI/CPC forecast still identifies a return to ENSO-neutral conditions by summer, with a 50 percent chance of transition to La Niña conditions later in 2016 (Fig. 3), but also points out that the spring predictability barrier will affect our certainty regarding ENSO-neutral vs. La Niña outlooks. The North American multi-model ensemble currently shows a strong event extending into early spring with gradual weakening to neutral conditions by early summer (Fig. 4).

This El Niño is not over; atmospheric and oceanic conditions are still indicative of a strong El Niño event. The CPC/IRI forecast noted this fact, stating that “El Niño is not done yet,” and that at a global scale, strong signals are still associated with El Niño, particularly in Brazil and southeast Asia (Fig. 5). In the southwestern U.S., we are nearing our dry season, meaning limited time remains for additional El Niño-influenced precipitation events of significance.

The IRI/CPC forecast also made note of the lack of “typical teleconnections” in this El Niño event. In the Southwest, for example, winter precipitation has been sparse following the storms of early January. These storms were exactly the sort of events expected in an El NIño year, but they were followed by a persistent ridge of high pressure that set up and limited the influx of additional moisture into the Southwest. This diverted moisture resulted in well above-average precipitation in the coastal northwestern U.S. and northern California, even while the Southwest was drier than normal (Fig. 6), a pattern which more closely aligns with La Niña. This occurred at an especially inopportune time in terms of southwestern climate patterns, as it effectively limited the opportunity for El Niño-associated storms during much of the the winter season. Sub-seasonal variability limited El Niño’s potential, and with the Southwest already characterized by dry conditions in a normal year, conditions that limit opportunities for precipitation can cut into seasonal totals significantly.

Next month’s issue will include a seasonal recap of El Niño and comparisons to seasonal averages as well as other El Niño events, but this high pressure ridge is likely one of the major reasons why the Southwest (and Arizona in particular) have not seen as frequent or as intense precipitation events as were forecast in seasonal outlooks. These forecasts and projections were dependent on the influence of a strong El Niño signal at a climate timescale (i.e., how these events cluster over years or decades), without the benefit of foresight of how a persistent high pressure ridge operating at a weather timescale (i.e., days or weeks) would knock the precipitation signal out of alignment for weeks on end.

2015-2016 El Niño Tracker - Feb 2016

Monday, February 22, 2016

Originally published in the Feb 2016 CLIMAS Southwest Climate Outlook


El Niño conditions continued for a 12th straight month, but we have passed the peak intensity of one of the strongest El Niño events on record. This does not mean that El Niño is over, though. Despite the recent warm and dry conditions in the Southwest, we are likely to see more weather events associated with El Niño conditions through spring 2016. In monitoring and forecast discussions, we continue to see persistent sea surface temperature (SST) anomalies (Figs. 1–2) and enhanced convective activity in the central and eastern Pacific, and most models forecast that this El Niño event will continue through spring or early summer. Precipitation and temperature outlooks mirror this forecast, calling for increased probabilities of precipitation across most of the southern U.S.

On Feb. 10, the Japan Meteorological Agency identified ongoing El Niño conditions as having passed their “mature” stage in the equatorial Pacific and predicted that this remarkably strong event would gradually weaken to neutral conditions by summer.  On Feb. 11, the NOAA-Climate Prediction Center (CPC) extended its El Niño advisory and identified the current atmospheric and oceanic anomalies as reflecting a strong El Niño that will persist through most of the spring before transitioning to ENSO-neutral conditions in late spring or early summer, with increasing chances of La Niña conditions by early fall. On Feb. 16, the Australian Bureau of Meteorology maintained its tracker at official El Niño status, but noted that deceasing temperature anomalies and building trade winds are indicators of this event’s gradual decline. On Feb. 18, the International Research Institute for Climate and Society (IRI) and CPC forecasts indicated a gradual weakening of El Niño from late spring into summer (Fig. 3), and reiterated that this El Niño would likely gradually decline, with lingering effects and impacts through spring 2016. The North American multi-model ensemble currently shows a strong event extending into early spring with gradual weakening to neutral conditions by late spring or early summer (Fig. 4).

In the Southwest, seasonal forecasts and past events suggested we should see well above-average cumulative precipitation totals throughout our cool season (Oct–Mar). However, the past 30–40 days of mostly warm and dry conditions, including numerous record-setting high temperatures combined with the melting of our previously abundant mountain snowpack, makes it hard not to feel like this El Niño is a “bust.” Is this a fair assessment, or does this simply reflect the difficulty of interpreting climate events (e.g., El Niño conditions) on a weather timeline? In previous discussions, we’ve highlighted the fact that we should expect periods of inactivity between storms, but we were hopeful those inactive periods would be on the order of days to a week, not weeks to a month. Even so, the default state for the desert Southwest is dry, so even a strong El Niño event can only alter that system so much, and past events do show periods of extended inactivity. Precipitation during the 1997–1998 El Niño event (strongest on record) was well below average in January 1998 (Fig. 5), with an extended run of dry days before it roared back to life from February through April 1998 (Fig. 6). If we look at cumulative cool-season precipitation during our current El Niño event (October 2015 – January 2016), our precipitation totals are at or above average (Fig. 7), and January 2016 was less dry than it may have seemed thanks to an active first week of the month (Fig. 8).

Even though the 2015–2016 El Niño event peaked in December 2015, the impacts in the Southwest lag behind this spike in intensity, which means we look to late winter and early spring as the most likely times for increased storm activity associated with the El Niño signal. We won’t be able to fully evaluate the 2015–2016 El Niño event until we know how much rain and snow fell over the entire cool season, and given past events, our best bets for seeing above-average precipitation will be in February and March. In the short term, we are left waiting for the jet stream to shift to a favorable pattern that funnels moisture into the Southwest, rather than directing it around us. 

Qué es ENSO - La Oscilación del Sur “El Niño”?

Thursday, January 28, 2016

“El Niño” y “La Niña” son parte de la oscilación del sur El Niño, (ENSO por sus siglas). ENSO es una fluctuación natural de las temperaturas superficiales del mar y la presión superficial del aire del Océano Pacifico Tropical entre el este y oeste.  Durante un evento “El Niño,” los vientos alisios del este se debilitan, permitiendo que el agua superficial más cálida  del Océano Pacifico Tropical del oeste corra  hacia el este.  Durante un evento “La Niña,”  estos vientos alisios se intensifican, causando que el agua cálida del este no pueda correr hacia el oeste y por consiguiente que el agua cálida superficial del este se apile.  Grandes áreas de baja presión superficial del aire y precipitación convectiva siguen el agua cálida al migrar a través del Océano Pacifico Tropical, alterando los patrones de circulación atmosférica (por ejemplo, la Circulación Walker), que pueden influir el tiempo de todo el mundo. (Figura 1)

Figura 1: Eventos El Niño causan que el pasaje invernal de la corriente en chorro  se mueva sobre la región del suroeste, generalmente entregando más lluvia y nieve invernal en la región. Imagen modificada de la Administración Oceánica y Atmosférica Nacional (NOAA).

El Niño Tracker - Jan 2016

Friday, January 22, 2016

El Niño conditions continued for an 11th straight month, putting us squarely in the middle of a strong El Niño event that will be among one of the strongest events on record. Forecasts focused on the persistence of sea surface temperature (SST) anomalies (Figs. 1–2) and weakened trade winds, enhanced convective activity in the central and eastern Pacific, and El Niño-related ocean-atmosphere coupling. Models continue to forecast a strong El Niño event that will last through spring 2016, but we are starting to see signs of decline in the overall strength of the event.

On Jan. 12, the Japan Meteorological Agency identified ongoing El Niño conditions as having reached their “mature stage” in the equatorial Pacific in November–December 2015, with likely gradual weakening during the months ahead. On Jan. 14, the NOAA-Climate Prediction Center (CPC) extended its El Niño advisory and said the current atmospheric and oceanic anomalies reflect a strong El Niño that will persist through most of the spring, transitioning to ENSO-neutral by late spring or early summer. The CPC noted, however, that the “exact timing of the transition is difficult to predict.” On Jan. 19, the Australian Bureau of Meteorology maintained its tracker at official El Niño status, with the event likely having peaked and ocean temperatures showing signs of gradual cooling. On Jan. 21, the International Research Institute for Climate and Society (IRI) and CPC forecasts indicated that all oceanic and atmospheric variables were indicative of a strong El Niño event, with consensus centering on strong El Niño conditions that will persist through spring 2016 (Fig. 3). The IRI/CPC briefing also indicated El Niño strength peaked in November–December, but that this was a “broad peak” with a gradual decline and the El Niño event would remain strong through late spring 2016. The North American multi-model ensemble currently shows a strong event extending into 2016 with gradual weakening heading into spring and summer (Fig. 4).

 

So what does this mean for the region? Even though forecasts are looking at the eventual decline of the El Niño signals, we are in the middle of a strong El Niño event. For the Southwest, the current seasonal forecasts and past events suggest we should see well above-average cumulative precipitation totals throughout our cool season (October–March), but we should also expect periods of inactivity between storms. Even though the 2015–2016 El Niño event “peaked” in November-December, we see impacts in the Southwest as they lag behind this spike in intensity, which means that we look to late winter and early spring as the most likely times to see increased storm activity associated with the El Niño signal. This doesn’t mean we can’t or won’t see increased activity outside of this window, but the default state for the desert Southwest is dry; even a strong El Niño event can only alter that system so much. We won’t be able to fully dissect and judge the 2015–2016 El Niño event until we see just how much rain and snow fell over the entire cool season. Given what we know about past events, our best bets for receiving above-average precipitation will be in February and March, or even April.  


Looking at the 1997–1998 event—the strongest El Niño event on record—most of Arizona and New Mexico received below-average rain and snowfall for all of January before returning to normal or above-normal precipitation in February and March (Figs. 5–8).

2015 - Eastern Pacific Tropical Storm Recap

Friday, December 18, 2015

The 2015 eastern Pacific tropical storm season was one of the most active seasons on record, with 18 named storms and 13 hurricanes, nine of which reached “major” hurricane status (category 3 or greater). We also saw the strongest hurricane on record, Patricia, in the eastern Pacific in late October, and the latest-forming major hurricane on record, Sandra, in late November (see NOAA’s National Hurricane Center for more details). This meets or exceeds the high end of the NOAA-Climate Prediction Center (CPC) seasonal forecast (from May 27), which predicted 15 to 22 named storms, seven to 12 hurricanes, and five to eight major hurricanes. The eastern Pacific hurricane forecast was tied to the ongoing El Niño forecast discussion, as conditions linked to El Niño (e.g., decreased wind shear in the tropical Pacific) also favored increased hurricane frequency and intensity in the Pacific region. Conversely, the Atlantic hurricane season was relatively quiet, with 11 named storms, four of which became hurricanes, including two major ones. This was mostly in line with NOAA-CPC projections of six to 10 named storms, one to four hurricanes, and up to one major hurricane. 

The season started off early and strong with two major hurricanes, Andres and Blanca, forming before June 1—Blanca brought considerable moisture into the Southwest—and Hurricane Carlos forming in early June. This start ran counter to the expected early season pattern in which hurricanes remain in the Pacific Ocean and generally head west. Few storms made direct landfall as hurricanes, but numerous systems made their presence felt by driving significant moisture into the Southwest, making substantial contributions to monthly seasonal precipitation totals. The season also was characterized by some relatively anomalous events, in particular, the record-breaking Patricia, which formed very quickly off the coast of Mexico before charging ashore in late October, and the late-forming Sandra. It remains difficult to provide direct attribution of El Niño as the primary cause of specific tropical storm events, but this elevated tropical storm activity and intensity are exactly the sort of patterns that we expect, given the influence that El Niño conditions were forecast to have on the eastern Pacific tropical storm season.

El Niño Tracker - Dec 2015

Friday, December 18, 2015

El Niño conditions continued for a 10th straight month, and models continue to forecast a strong El Niño event that will last through spring 2016 and remain strong through the early part of the year. Forecasts focused on the persistence of sea surface temperature (SST) anomalies (Figs. 1–2) and weakened trade winds, enhanced convective activity in the central and eastern Pacific, and El Niño-related ocean-atmosphere coupling. Notably, the SST values in the Niño 3.4 region were at or above the record values in November. Climate scientists have been quick to point out that numerous factors contribute to the overall strength of El Niño, but we are certainly seeing one of the strongest events on record.

Image Source - Australian Bureau of Meteorology

Image Source - NOAA/NWS - Climate Prediction Center

On Dec. 8, the Australian Bureau of Meteorology maintained its tracker at official El Niño status, with the event having likely reached its peak. On Dec. 10, the Japan Meteorological Agency identified ongoing El Niño conditions as having reached their “mature stage” in the equatorial Pacific and “remarkably above-normal” SST anomalies and atmospheric convective activity. The agency projected that El Niño would remain in place through spring 2016 before transitioning to ENSO-neutral by summer. Also on Dec. 10, the NOAA-Climate Prediction Center (CPC) extended its El Niño advisory and identified the current atmospheric and oceanic anomalies as reflecting a strong El Niño event that will be one of the three strongest events on record. CPC models indicate the El Niño event will persist through winter, with a transition to ENSO-neutral conditions by late spring or early summer. On Dec. 17, the International Research Institute for Climate and Society (IRI) and CPC forecasts indicated that all oceanic and atmospheric variables were indicative of a strong El Niño event, with consensus centering on strong El Niño conditions that will persist through spring 2016 (Fig. 3).   The North American multi-model ensemble currently shows a strong event extending into 2016 with gradual weakening heading into spring (Fig. 4).

Image Source - International Research Institute for Climate & Society

Image Source - NOAA/NWS - Climate Prediction Center

So what does this mean for the region? Seasonal forecasts and past events suggest we should see well above-average cumulative precipitation totals throughout our cool season, but we should also expect periods of inactivity between storms. Past events also suggest the best bets for seeing above-average precipitation will be in February and March, and perhaps later in January. Looking at the 1997–1998 event—the strongest El Niño event on record—most of Arizona and New Mexico received above-average precipitation in December but below-average rain and snowfall for all of January before returning to normal or above-normal precipitation in February and March (Figs. 5–8). At this point, we know a strong El Niño event is underway, and it will likely have a number of projected impacts on the Southwest (and the world), but we will need to wait until seasonal totals are in to accurately gauge the impact of El Niño.

Image Source - Western Regional Climate Center - WestWide Drought Tracker

Image Source - Western Regional Climate Center - WestWide Drought Tracker

Image Source - Western Regional Climate Center - WestWide Drought Tracker

Image Source - Western Regional Climate Center - WestWide Drought Tracker


To provide data and analysis regarding possible impacts of El Niño on the Southwest, CLIMAS created an El Niño hub: climas.arizona.edu/sw-climate/el-niño-southern-oscillation

Please contact Dan Ferguson or Ben McMahan for more information

El Niño and Vector Borne Disease - What do we know about mosquitos, disease, and climate?

Monday, December 14, 2015

We are usually able to enjoy the patio by October, but the mosquitoes were still biting. What does the science tell us about El Niño and mosquito-borne disease? Short answer: it’s complicated. 

With respect to mosquito-borne disease, we tend to think about a mosquito season; the period of the year during which mosquitoes are active. For diseases like West Nile virus, the cycle starts when mosquitoes bite birds, infecting them with the disease. Eventually, often in late summer and early fall, enough mosquitoes and birds are infected that the disease spills over into human and horse populations. This requires that there are enough infected mosquitoes and that these mosquitoes survive long enough to become infectious and bite humans or horses. 

That gets us back to the mosquito-season. Immature mosquitoes—egg, larval, and pupal stages—require water to compete their life cycle. This water is provided both by precipitation and by human behavior, collecting in green pools, unprotected water storage, clogged gutters, or saucers under plants. Temperature drives how quickly an immature mosquito becomes an adult; typically, warmer temperatures speed up development. Another important piece is adult mosquito survival and host-seeking activity, both of which are mediated by humidity. Thus, the duration and intensity of any year’s mosquito season is going to be strongly influenced by temperature and precipitation. 

This year, with respect to precipitation, we had a wet June but then a normal July–September rainfall. The rains are expected to remain above-average through the winter. Despite the mosquitoes we experienced this summer and fall, the implications of the summer lull in precipitation are unknown. Because of the ramping up of West Nile virus in the bird-mosquito cycle, we might actually escape a bad year and hopefully, the bird-mosquito transmission cycle was broken and won’t have enough time (enter the effect of cooler winter temperatures) for it to build up again and spill over to humans. 

Research results are mixed, being highly dependent on the disease of concern and the region of study. Intuitively we know there must be an association between climate and vector life cycles, as the life cycle of invertebrates are often tightly associated with weather. However, with urban mosquitoes like the Culex species that transmit West Nile in the United States and the Aedes species that transmit dengue and chikungunya, human behavior plays a role in mediating exposure to mosquitoes, the availability of breeding sites, and even mosquito survival. Moreover, the diseases themselves have an intrinsic intra-annual cycle in which the proportion of a given population that is susceptible to infection fluctuates between years, confounding the climate-driven associations with temperature and precipitation. 

That leaves us with a dissatisfying ‘we don’t know’ and ‘it all depends.’ Our experience will depend on the previous years’ mosquito abundance, previous years’ human or other host disease occurrence, current human or other host susceptibility, and the duration of the anomalous weather. It does leave us with a positive message, though: what we do as individuals does matter. Protect yourself from mosquitoes, empty breeding sites, cover your water storage, repair your window screens, and use mosquito repellent when you go out of doors. 

El Niño Tracker - Nov 2015

Saturday, November 21, 2015

Originally published as part of the Nov 2015 CLIMAS Southwest Climate Outlook

El Niño conditions continued for a ninth straight month, and models continue to forecast a strong El Niño event that likely will last through spring 2016 and remain strong through the early part of the year. Forecasts focused on the persistence of sea-surface temperature (SST) anomalies (Figs.1–2) and weakened trade winds, enhanced convective activity in the central and eastern Pacific, and El Niño-related ocean-atmosphere coupling.

Image Source - Australian Bureau of Meteorology

Image Source - NOAA/NWS - Climate Prediction Center

On Nov 10, 2015, the Japan Meteorological Agency identified ongoing El Niño conditions in the equatorial Pacific, and in particular “remarkably above normal” SST anomalies and atmospheric convective activity, with projections that El Niño would remain in place through spring 2016. On Nov 10, 2015, the Australian Bureau of Meteorology maintained its tracker at official El Niño status, remarking on the persistent strength of oceanic and atmospheric indicators. On Nov 12, 2015, the NOAA-Climate Prediction Center (CPC) extended its El Niño advisory, and identified the current atmospheric and oceanic anomalies as reflecting “a strong and mature El Niño episode”.  Their models indicate the El Niño event will persist through winter, with a transition to ENSO neutral conditions by late spring or early summer. On Nov 19, the International Research Institute for Climate and Society (IRI) and CPC forecasts indicated that both sea surface temperature anomalies and atmospheric variables were indicative of a strong El Niño event, with consensus centering on strong El Niño conditions that might strengthen even more into early winter 2015-2016, before gradual weakening into spring 2016 (Fig. 3). 

Image Source - International Research Institute for Climate & Society

The North American multi-model ensemble currently shows a strong event extending into 2016 with gradual weakening heading into spring (Fig. 4). The ocean and atmosphere are indicative of a strong El Niño event that shows no sign of weakening, and current forecasts that have it pegged as one of the strongest events on record.  There is little doubt that El Niño will remain on the current trajectory in the near term, and we will see one of the top three strongest events on record since 1950.

Image Source - NOAA/NWS - Climate Prediction Center

What does this mean for the Southwest? Seasonal forecasts and past events suggest we should see well above-average cumulative precipitation totals over the cool season.  We should not expect a winter of daily rains, however, as there will likely be periods of inactivity between storms.  Looking at the 1997–1998 event—the strongest El Niño event on record—most of Arizona and New Mexico received above-average precipitation in December but below-normal precipitation for all of January before returning to normal or above-normal precipitation in February and March (Figs. 5–8).

Image Source - Western Regional Climate Center - WestWide Drought Tracker

Image Source - Western Regional Climate Center - WestWide Drought Tracker

Image Source - Western Regional Climate Center - WestWide Drought Tracker

Image Source - Western Regional Climate Center - WestWide Drought Tracker

In order to track this variability and provide data and analysis regarding possible impacts of El Niño on the Southwest, CLIMAS has created an El Niño hub. This is our repository for news and information about the expected impacts of El Niño, from the perspective of what is most relevant and applicable to the Southwest. This includes what we have learned from past El Niño events, and what forecasting and models can tell us about planning for the ongoing event.

2015 Monsoon Recap - Oct 2015

Friday, October 16, 2015

Originally published in the October 2015 CLIMAS Southwest Climate Outlook

The monsoon started strong in late June and early July. This early start centered on Arizona, which recorded its second wettest June on record (Fig. 1a), with a return to relatively normal rainfall totals in July. New Mexico saw an increase in precipitation, recording its 10th wettest July on record (Fig. 1b). Following a break in the monsoon circulation, rainfall in August and September was average in Arizona and below average for New Mexico (Figs. 1c-1d).  These statewide rankings do little to capture the spatial and temporal variability of the monsoon (see below), but they do give a sense as to the general character of the monsoon.  As noted in the October SW Climate Podcast, the monsoon started strong, but tended to fizzle for most of August and September. However we did see a late season push from tropical storm activity, which helped push some of the monsoon seasonal precipitation totals just above average values.  

Image Source - NOAA - National Centers for Environmental Information

Shifts in the persistence and intensity of the monsoon are tied to the strength and location of the monsoon ridge, which, depending on its location, can facilitate the flow of organized storm activity from the south or east (during increased monsoon activity), or can shift the flow such that we see extended periods of decreased precipitation. The weakening of the monsoon ridge since early July is likely due at least in part to increasing El Niño convection. With this El Niño event set to be one of the strongest on record, it is not surprising that it may have had an expected disruptive effect on monsoon circulation. 

A particularly notable characteristic of the monsoon this year was the persistently above average dewpoint temperatures we saw over the season (Fig. 2).  This was likely linked to eastern Pacific tropical storm activity driving moisture into the region. In some cases, this provides a supplement to monsoon precipitation, as we saw this year with Linda, 16-E (and last year with Norbert and Odile). These storms can have intense and spatially variable effects, including increased precipitation and serious flooding, as well as driving up the humidity while adding little additional precipitation.

Image Source - National Weather Service

Monsoon Summary (June 15 - Sept 30)

Looking at cumulative totals for the 2015 monsoon, precipitation as a percent of average demonstrates the spatial variability of monsoon precipitation (Figs. 3a–b), while raw precipitation totals show the wide range of normal precipitation totals we see across the Southwest (Figs. 4a–b). These totals can be skewed by a few strong events or even a single strong storm; the percent of days with rain (Figs. 5a–b) highlights the regularity of monsoon precipitation thus far, with much of Arizona and nearly all of New Mexico recording rain events (greater than 0.01 inch) on at least 25 percent of days since June 15. The daily intensity index (Figs. 6a–b) further illustrates the steady nature of most of this monsoon precipitation; higher values indicate much of the rain fell in a single event and lower values indicate more frequent and less intense events.

Image Source - Climate Science Applications Program

El Niño Tracker - Oct 2015

Thursday, October 15, 2015

Originally published in the Oct 2015 CLIMAS Southwest Climate Outlook

We spent the better part of 2014 (and the first part of 2015) waiting in anticipation for an El Niño event that was initially forecast to be one of the stronger events on record. By early 2015, the event in question had not yet materialized, and some questioned whether El Niño would ever arrive. Eventually it did, and has been going strong for months, with most forecasts indicating that it will remain a strong event through the winter. As this event unfolds, there are numerous impacts we might expect to see across the Southwest over the course of our cool season (approximately Oct - Mar). In the coming months, CLIMAS will aggregate news, information, and commentary about the possible and expected impacts of El Niño, from the perspective of what is most relevant and applicable to the Southwest. This will include what we have learned from past events, and what forecasting and models can tell us about planning for this event.

For more information, please visit our repository for ENSO related materials, which we will update with timely and relevant information about El Niño throughout the winter.


2015 El Niño Tracker

El Niño conditions continued for an eighth straight month, and models continue to forecast a strong El Niño event that likely will last through spring 2016 and remain strong through the early part of the year. Forecasts focused on the persistence of sea-surface temperature (SST) anomalies (Figs.1–2) and weakened trade winds, enhanced convective activity in the central and eastern Pacific, and El Niño-related ocean-atmosphere coupling.

Image Source - Australian Bureau of Meteorology

Image Source - NOAA/NWS - Climate Prediction Center

On October 8, the NOAA-Climate Prediction Center (CPC) extended its El Niño advisory, predicting a 95 percent chance that the current strong El Niño conditions will continue through winter 2015–2016, with gradual weakening into spring 2016 (Fig. 3). The center cited persistent positive SST anomalies in the central and eastern Pacific and ongoing ocean-atmospheric coupling and convection activity as indicators of an ongoing and strengthening event. On October 9, the Japan Meteorological Agency identified ongoing El Niño conditions in the equatorial Pacific, noting “remarkably above-normal” SST anomalies and convective activity, and forecast the current El Niño conditions would continue into spring. On October 13, the Australian Bureau of Meteorology maintained its tracker at official El Niño status, noting the strongest event seen since 1997, and forecast the event will persist into early 2016. On October 15, the International Research Institute for Climate and Society (IRI) and CPC forecasts indicated a 100 percent chance of El Niño through early 2016, and saw continued evidence in both the ocean and atmosphere that this event would be one of the strongest events on record.

Image Source - International Research Institute for Climate & Society

The North American multi-model ensemble currently shows a strong event extending into 2016 with gradual weakening heading into spring (Fig. 4). We continue to grapple with this El Niño event and the potential impacts it might bring to the Southwest over the winter and into spring, especially given current forecasts that have it pegged as one of the strongest events on record. Seasonal forecasts (see Fig. 5 on Maps Page) and past events suggest we might expect well above-average precipitation totals across our cool season. This does not mean we should expect a winter of daily rains, however. Variability across these months means we may see periods of below-average precipitation as well. 

Image Source - NOAA/NWS - Climate Prediction Center

Looking at the 1997–1998 event—the strongest El Niño event on record—most of Arizona and New Mexico received above-average precipitation in December but below-normal precipitation for all of January before returning to normal or above-normal precipitation in February and March (Figs. 5–8). At this point, we are fairly certain that El Niño will remain on the current trajectory, and we will see one of the top three strongest events on record since 1950. This is likely to bring above-average winter precipitation to the Southwest, particularly later in the season, but it is far from a guarantee. Additionally, what happens in late spring and early summer may determine the longer-term impacts. If we bounce back into La Niña conditions, as happened after the 1997–1998 event, we may see a return to more below-average precipitation forecasts heading into 2016–2017. 

Image Source - Western Regional Climate Center - WestWide Drought Tracker

Image Source - Western Regional Climate Center - WestWide Drought Tracker

Image Source - Western Regional Climate Center - WestWide Drought Tracker

Image Source - Western Regional Climate Center - WestWide Drought Tracker

El Niño is here…what exactly does that mean for Arizona and New Mexico?

Thursday, September 24, 2015

“El Niño” has been all over the news lately, even garnering comparisons to a Godzilla – a prehistoric sea monster awakened and empowered by nuclear radiation (thank you Wikipedia). This characterization is in response to the near record strength of this El Niño event, which is exciting for climate enthusiasts, but leaves most people wondering; what does a strong El Niño event actually mean for Arizona and New Mexico? Are we talking floods? Droughts?  Plagues of locusts? Additionally, how soon can we expect this “El Niño” character to show up?  In other words, what does a realistic assessment look like?

First of all, El Niño is not a singular weather event that will storm ashore on a particular date.  Climate.gov has come up with an excellent analogy – tying the effects of El Niño to a big construction project - you will definitely feel the effects, but these vary with space and time and are dependent on a number of factors. There are a number of El Niño primers (e.g. the climate.gov ENSO blog) that explain how El Niño works in technical terms, but to put it simply, El Niño is part of the El Niño-Southern Oscillation (ENSO) which is a semi-regular shift on the order of several years (Figure 1, Oceanic Niño Index) in sea surface temperatures, atmospheric pressure, and rainfall patterns, along the equator in the Pacific Ocean. These shifts (between El Niño and La Niña event) reorganize global weather patterns that can drive drought and flood patterns on a regional basis.

Our understanding of the global impact of El Niño events has improved considerably over the last few decades. In particular, we can often detect the development of an El Niño event months in advance, long before it will ever have an impact on seasonal weather conditions.  For Arizona and New Mexico, an El Niño event means increased probability of receiving above-average winter precipitation, generally between October and March. However, there is still plenty of variability when comparing El Niño events, and there is no guarantee that any given El Niño event will lead to wetter than average conditions.

In order to look more closely at this relationship, it helps to take a look at plots describing the relationship between past El Niño and La Niña events, and October-March total precipitation for select regions in Arizona and New Mexico.[1] A couple key points:

  1. We will be looking at precipitation totals within climate divisions, which represent average values over large multi-county areas (Figure 2, AZ & NM Climate Divisions).  These totals are calculated using station observations within these regions. 
  2. We will be using a simple metric called the Oceanic Nino Index (ONI) to assess the phase and strength of ENSO. The ONI describes temperature anomalies (warm or cool) in the central and eastern Pacific Ocean along the equator, which in turn relates to shifts in tropical thunderstorm activity and resultant impacts to global atmospheric circulation

Figures 3a & 3b compare the ENSO-precipitation relationship for two regions in Arizona (climate division 3 and climate division 7).  Total cool-season precipitation is on the y axis, and the average ONI value for the same Oct-March period is on the x axis. The dots are color coded: red to reflect El Niño events (ONI values > 0.5), blue for La Niña events (ONI values < -0.5), and green for ENSO neutral years (ONI between -0.5 and 0.5).. At first glance, the blue dots (La Niña years) are clustered much lower on the y-axis, while the red dots (El Niño years) are much higher on this axis.  This characterizes the historical connection between La Niña events and dry winters, while El Niño years are associated with wet winters. The horizontal lines on the plots are the average cool-season precipitation for all years (black line), La Niña years (blue line), and El Niño years (red line), and help illustrate this relationship further. 

The more you stare at this graph (trust me, we’ve done our share of staring!), the more you see that this relationship is complicated, and even varies between the two regions in Arizona. In general there is a relationship between the ONI index value and the amount of cool-season precipitation (see correlation values on each figure), but this relationship is noisy at best, and demonstrates that the strength of the ENSO phase (in this case using ONI) isn’t a perfect linear fit with total cool season precipitation. Some of the biggest outliers are linked to weak or even moderate strength El Niño events, but are associated with below average winter precipitation (We're looking at you, 2007).  This is especially evident as you move north in the region (see climate division #3), where the relationship between El Niño strength and cool season precipitation is even weaker. What’s the point of all this?  El Niño is not a slam dunk forecast for unusually wet cool season conditions for the Southwest.

But…this year we are in rare territory with respect to the current and forecasted strength of this El Niño event. Current forecast models indicate that ONI values should reach approximately 2 deg C (above normal) over the upcoming winter season, making it one of the strongest El Niño events on record and on par with past big events like 1982-83 and 1997-98. When we look for these years on the plots in figure 2, we see that both of these years were associated with above-average precipitation.  In fact, the three “strong” events (1973, 1983, 1998) and the as well as the five “moderate” years (1958, 1966, 1987, 1992, 2010) all saw above average precipitation, which means that as long as this event stays strong (all indications are that it will) we will likely see a wetter than average winter.  A large caveat being the sample size of this relationship is VERY small.  

This pattern is even stronger for climate division 7 (southern Arizona) where the overall relationship between ONI and cool season precipitation is stronger. This is consistent with observations that the relationship between ENSO and winter precipitation is stronger over southern parts of Arizona (Figure 4, Percent of normal winter precipitation 1983 & 1998) and New Mexico. This can be attributed to a stronger than average and more persistent sub-tropical jet stream that favors southern Arizona and New Mexico with above-average winter storm activity. 

The current seasonal precipitation forecasts for the upcoming winter season issued by the NOAA Climate Prediction Center also reflect this expectation for additional moisture, especially in the SW. The best chances for observing above-average winter precipitation cover all of Arizona and New Mexico, but are slightly better for the southern half of each state. There is a pretty good chance that the next red dot for this upcoming year that shows up on these plots will be above-average for most climate divisions across the Southwest, but how much above-average will be very interesting to see.


[1] We are borrowing this idea from the Western Regional Climate Center.

Monsoon Summary Jun 15-Sep 17

Saturday, September 19, 2015

The monsoon started strong in late June and early July. This early start centered on Arizona, which recorded its second wettest June on record (Fig. 1a), with a return to relatively normal rainfall totals in July. New Mexico saw an increase in precipitation, recording its 10th wettest July on record (Fig. 1b). Rainfall in August and September was mostly below average, which is characteristic of the North American monsoon’s sporadic and spatially limited precipitation events.

These shifts in persistence and intensity are tied to the strength and location of the monsoon ridge, which, depending on its location, can facilitate the flow of organized storm activity from the south or east (during increased monsoon activity) or can shift the flow such that we see extended periods of decreased precipitation. The later season weakening of the monsoon ridge since early July is likely due at least in part to increasing El Niño convection. With this El Niño event set to be one of the strongest on record, it is not surprising that it may have had an expected disruptive effect on monsoon circulation. We also continue to watch eastern Pacific tropical storm activity as it helps drive moisture into the region, a pattern we’ve seen repeatedly in the past few weeks with a number of tropical storm systems, particularly Linda. The effects of these systems can be intense and spatially variable, with southern Arizona experiencing increased humidity and little additional precipitation, compared to serious flooding in northern Arizona and southern Utah. Regional dewpoint readings also illustrate the variability of monsoon activity and the influence of tropical storm activity (Fig. 2).

Looking at cumulative totals to date for the 2015 monsoon, precipitation as a percent of average demonstrates the spatial variability of monsoon precipitation (Figs. 3a–b), while raw precipitation totals show the wide range of normal precipitation totals we see across the Southwest (Figs. 4a–b). These totals can be skewed by a few strong events or even a single strong storm; the percent of days with rain (Figs. 5a–b) highlights the regularity of monsoon precipitation thus far, with much of Arizona and nearly all of New Mexico recording rain events (greater than 0.01 inch) on at least 25 percent of days since June 15. The daily intensity index (Figs. 6a–b) further illustrates the steady nature of most of this monsoon precipitation; higher values indicate much of the rain fell in a single event and lower values indicate more frequent and less intense events.

El Niño Tracker - September 2015

Friday, September 18, 2015

El Niño conditions continued for a seventh straight month, and forecasts and models indicate this event likely will last through spring 2016, remaining strong through the early part of the year. Forecasts focused on the persistence of sea-surface temperature (SST) anomalies (Figs.1–2) and weakened trade winds, ongoing convective activity in the central and eastern Pacific, and El Niño-related ocean-atmosphere coupling.

On September 10, the Japan Meteorological Agency identified persistent El Niño conditions in the equatorial Pacific, especially SST anomalies and convective activity, and forecast that the current El Niño conditions were likely to persist through winter. That same day, the NOAA-Climate Prediction Center (CPC) extended its El Niño advisory, predicting a 95 percent chance that El Niño will continue through winter 2015–2016, with gradual weakening into spring 2016 (Fig. 3). The center cited persistent positive SST anomalies in the central and eastern Pacific and ongoing ocean-atmospheric coupling and convection activity as indicators of an ongoing and strengthening event. On September 15, the Australian Bureau of Meteorology maintained its tracker at official El Niño status; a strong event with the potential to exceed the 1997–1998 El Niño in strength. On September 17, the International Research Institute for Climate and Society (IRI) and CPC forecasts corroborated the forecast of a strong El Niño with the potential to rival the strongest events on record.

The North American multi-model ensemble currently shows a strong event extending into 2016 (Fig. 4). Emergent questions have centered on how this event compares to other strong events such as those in 1982–83 and 1997–98. If El Niño remains on this trajectory, it will likely be one of the top three strongest events on record since 1950. Sensationalistic media coverage already has started but it will be important to temper expectations without minimizing possible impacts. Forecast consensus is for a strong El Niño that extends into winter 2015–2016 and would likely bring above-average winter precipitation in the Southwest, particularly later in the season. It is important to note that this relationship suggests that a strong El Niño event gives the Southwest a much better chance at increased precipitation totals by March or April, but it is far from a guarantee of increased precipitation. In the more immediate future, El Niño conditions could lead to a repeat of 2014’s above-average eastern Pacific tropical storm season, when conditions favorable to El Niño were thought to be driving increased tropical storm activity in the Southwest in September and October.

El Niño Tracker - August 2015

Friday, August 21, 2015

Originally published in the August 2015 CLIMAS Southwest Climate Outlook

El Niño conditions continued for a sixth straight month and forecasts and the most recent outlooks offer a consistent cluster of forecasts calling for a clear El Niño signal similar to past strong events, lasting into early 2016. Forecasts focused on the persistence of sea-surface temperature (SST) anomalies (Figs.1–2) and on weakened trade winds, ongoing convective activity in the central and eastern Pacific, and El Niño-related ocean-atmosphere coupling.

Image Source - Australian Bureau of Meteorology

Image Source - National Climatic Data Center

On August 10, the Japan Meteorological Agency identified persistent El Niño conditions in the equatorial Pacific, especially SST anomalies and convective activity, and forecast that the current El Niño conditions were likely to persist until winter. On August 13, the NOAA-Climate Prediction Center (CPC) extended its El Niño advisory, predicting more than a 90-percent chance that El Niño will continue through winter 2015–2016 and an 85-percent chance it will last into early spring 2016 (Fig. 3). The center cited persistent positive SST anomalies in the central and eastern Pacific and ongoing ocean-atmospheric coupling and convection activity as indicators of an ongoing and strengthening event. On August 18, the Australian Bureau of Meteorology maintained its tracker at official El Niño status, identifying a strengthening El Niño with strong ocean-atmosphere coupling and projecting the event is likely to persist into 2016. On August 20, the International Research Institute for Climate and Society (IRI) and CPC forecasts indicated the persistence of strong El Niño conditions, with possible further strengthening during fall 2015, and extending well into spring 2016. The North American multi-model ensemble currently shows a strong event extending into 2016 (Fig. 4).

Image Source - International Research Institute for Climate and Society

Image Source - NOAA - Climate Prediction Center

Given that the current and projected strength of the El Niño is strong with no sign of weakening, emergent questions have centered on how this event compares to other strong events such as those in 1982–83 and 1997–98. Limited data makes comparisons and statistical analyses more difficult, and each event has a unique context that affects its impact. If El Niño remains on this trajectory, it most likely will be one of the top three or four strongest events on record since 1950, with implications for both Southwest and global communities. Sensationalistic media coverage already has begun (see recent coverage of “Godzilla” El Niño), but it will be important to temper expectations without minimizing possible impacts. 

The general consensus is that a strong El Niño extending into winter 2015–2016 would likely bring above-average winter precipitation in the Southwest (Fig. 5), particularly later in the season. It is important to note that this relationship suggests that a strong El Niño event gives the Southwest a much better chance at increased precipitation totals by March or April, but it is far from a guarantee of increased precipitation. Current CPC forecsts do indicate increased an chance of precipitation in late fall and early winter, but the region could very well see a relatively dry period through early 2016 following the close of the eastern Pacific tropical storm season; this would not necessarily mean that El Niño was a “bust.” In the more immediate future, El Niño conditions could lead to a repeat of 2014’s above-average eastern Pacific tropical storm season, when conditions favorable to El Niño were thought to be driving increased tropical storm activity in the Southwest in September and October.

Image Source - NOAA Climate.gov

Monsoon Summary Jun 15-Aug 20

Friday, August 21, 2015

Originally published in the August 2015 CLIMAS Southwest Climate Outlook

The monsoon started off early and strong with several widespread thunderstorms in late June and early July, especially in Arizona, which recorded its second wettest June on record.  Precipitation tapered to some extent in July in Arizona but continued to be frequent and widespread in New Mexico, which recorded its 10th wettest July on record (Figs. 1a-2a).  

Overall monsoon activity has taken a break thus far in August, although a few powerful and localized storms brought significant precipitation to portions of Arizona. This pattern is a defining characteristic of the 2015 monsoon, particularly in Arizona, where many of the monsoon storms have been highly localized, dropping heavy precipitation in smaller areas and often on high elevation peaks instead of more widespread and systematic monsoon activity. Portions of southern Arizona and the Four Corners region—areas that saw considerable precipitation deficits in the past few years—have been the beneficiaries of this variable coverage, especially in the past few weeks. This pattern may change if the monsoon ridge sets up further east, allowing for more organized storm activity to flow in from the south in the coming weeks, or if later-season eastern Pacific tropical storm activity ramps up and helps drive moisture into the region. 

We also have seen some weakening of the monsoon ridge since July 5, likely due to El Niño convection picking back up, but it remains to be seen what the overall impact of El Niño will be on this year’s monsoon. Regional dewpoint readings also illustrate the variability of monsoon activity, particularly in July and into August (Fig. 2).

In the first two months of the monsoon, most of northern Arizona and nearly all of New Mexico recorded above-average precipitation (Figs. 3a–b), albeit with a wide range of precipitation totals across the region (Figs. 4a–b). Southwestern Arizona, particularly the southwest and northwest corners, are notable exceptions to this pattern, although these areas typically receive far less monsoon precipitation overall. The percent of days with rain highlights the regularity of monsoon precipitation thus far, with much of eastern Arizona and nearly all of New Mexico recording rain events (greater than 0.01 inch) on 35 to 50 percent of days since June 15 (Figs. 5a–b). The daily intensity index (Figs. 6a–b) further illustrates the steady nature of most of this monsoon precipitation; higher values indicate much of the rain fell in a single event and lower values indicate more frequent and less intense events.

El Niño Tracker - July 2015

Monday, July 20, 2015

El Niño conditions continue for a fifth straight month, and at this point, forecasters are relatively bullish that we are witnessing the development of a moderate-to-strong event that could rival 1997 in absolute magnitude later this year. The most recent outlooks from various sources offer a consistent cluster of forecasts calling for a clear El Niño signal that is maintained or even strengthens well into early 2016. Forecasts focused on the persistence of sea-surface temperature (SST) anomalies (Figs.1 - 2) along with weakening trade winds, ongoing convective activity in the central and eastern Pacific, and El Niño-related ocean-atmosphere coupling.

On July 7, the Australian Bureau of Meteorology maintained its tracker at official “El Niño” status, identifying a strengthening El Niño (in part due to increased tropical storm activity), and projecting the event as likely to persist through the end of 2015 and into 2016. On July 10, the Japan Meteorological Agency identified strengthening El Niño conditions in the equatorial Pacific, and forecast that the current El Niño conditions were likely to last until winter. On July 9, the NOAA-Climate Prediction Center (CPC) extended its El Niño advisory with a greater than 90-percent chance that El Niño will continue through winter 2015-2016, and an 80-percent chance it will last into early spring 2016. It cited the increasingly positive SST anomalies in the central and eastern Pacific and ongoing ocean-atmospheric coupling and convection activity as indicators of an ongoing and strengthening event (Fig. 3). On July 16, the International Research Institute for Climate and Society (IRI) and CPC forecasts indicated continued strengthening of El Niño through 2015 and into 2016, with a moderate event likely becoming a strong event by summer or early fall and lasting into early 2016. The North American multi-model ensemble currently shows a moderate event extending through early summer, with potential for a strong event by mid-summer or early fall (Fig. 4).

It is clear that we are in the midst of an ongoing and strengthening El Niño event.  If this event remains on the current trajectory, it could surpass the strongest El Niño events of recent decades (1997 in particular), with implications for both Southwest and global communities. 

In May and early June, we witnessed exactly the sort of patterns we might expect to see in Arizona and New Mexico under El Niño conditions—above-average precipitation and below-average temperatures. If El Niño persists into winter 2015-2016, particularly if it remains a moderate-to-strong event, we would likely continue to see above-average precipitation in the Southwest (Fig. 5). Although the presence of El Niño conditions often has been associated with a delay in the start of the monsoon, this year the monsoon began early. However, a resurgent El Niño signal now may be pushing back and could work to disrupt the monsoon ridge, leading to one or more ‘breaks’ in the monsoon. The event could also lead to a repeat of 2014’s above-average eastern Pacific tropical storm season, when conditions favorable to El Niño were thought to be driving increased tropical storm activity in the Southwest in September and October.

Image Source - Australian Bureau of Meteorology

Image Source - National Climatic Data Center

Image Source - International Research Institute for Climate and Society

Image Source - NOAA - Climate Prediction Center

Image Source - NOAA Climate.gov

Monsoon Summary - (June 15 - July 16)

Thursday, July 16, 2015

After a few anomalous incursions of tropical moisture in early June, we saw an early beginning to the monsoon in mid- to late June, a few weeks ahead of the typical start date (Fig. 1). Regional dewpoint/humidity readings for June illustrate the multiple incursions of tropical moisture, followed by the onset of monsoon conditions later in the month (Fig. 2).

The monsoon ridge was able to set up early, leading to a number of precipitation events (including above-average precipitation) across the Southwest starting in the last week of June. As recently as last month, we had been anticipating a delayed start to the monsoon, as El Niño conditions tend to suppress its onset. However, the opposite occurred, possibly due to a record-strong Madden Julian Oscillation (MJO) pattern that temporarily suppressed El Niño’s typical influence on the subtropical ridge. We have seen some weakening of the monsoon ridge since July 5, likely due to El Niño convection picking back up, but it remains to be seen what the overall impact of El Niño will be on this year’s monsoon.

In the first month of the monsoon, most of New Mexico and much of eastern Arizona received well-above-average precipitation (Fig. 3a-b), albeit with a wide range of precipitation totals across the region (Fig. 4a-b). Western Arizona (particularly the southwest and northwest corners) are notable exceptions to this pattern, although these regions typically receive far less monsoon precipitation overall.  The percent of days with rain highlights the regularity of monsoon precipitation thus far, with much of eastern Arizona and most of New Mexico recording rain events (>0.01”) on 35-50 percent of days since Jun 15 (Fig. 5a-b). The daily intensity index (Fig. 6a-b) further illustrates the steady nature of most of this monsoon precipitation, where higher values indicate much of the rain fell in a single event and lower values indicate more frequent and less intense events.

El Niño Tracker - June 2015

Friday, June 19, 2015

Originally Published in the June 2015 CLIMAS SW Climate Outlook (SWCO)


El Niño conditions continued for a fourth straight month with no signs of weakening or disorganizing. Forecasts focused on the persistence of sea-surface temperature (SST) anomalies (Figs.1 - 2) along with weakening trade winds, ongoing convective activity, and El Niño-related ocean-atmosphere coupling. Despite the high degree of uncertainty associated with forecasting El Niño this time of year (the so-called spring predictability barrier), the most recent outlooks from various sources offer a consistent cluster of forecasts calling for a clear El Niño signal that is maintained or even strengthening. 


Image Source - Australian Bureau of Meteorology


Image Source - National Climatic Data Center

On June 9, the Australian Bureau of Meteorology maintained its tracker at official “El Niño” status, identifying persistent SST anomalies, weak trade winds, and ocean-atmospheric coupling as indicators this El Niño event was strong enough to extend through 2015. On June 10, the Japan Meteorological Agency identified strengthening El Niño conditions in the equatorial Pacific, and forecast that the current El Niño conditions were likely to last until winter. On June 11, the NOAA-Climate Prediction Center (CPC) extended its El Niño advisory with a 90 percent chance that El Niño will continue through fall 2015 and an 85 percent chance the event would last through winter 2015-2016.  It pointed to the increasingly positive SST anomalies, along with ongoing ocean-atmospheric coupling and dateline convection activity, as indicators of an ongoing and strengthening El Niño event (Fig. 3). On June 18, the International Research Institute for Climate and Society (IRI) and CPC forecasts indicated continued strengthening of El Niño through 2015, with a moderate event during summer and likely stronger in the fall, lasting into early 2016. The North American multi-model ensemble currently shows a moderate event extending through early summer, with potential for a strong event by mid-summer or early fall (Fig. 4).


Image Source - International Research Institute for Climate and Society


Image Source - NOAA - Climate Prediction Center

Last year’s vacillating signals and forecasts may have led forecasters to take a more conservative approach when presented with similar conditions earlier this year to avoid repeating the “enthusiastic” forecasts of Spring 2014 that didn’t immediately pan out.  That said, we appear to be in the midst of an ongoing and strengthening El Niño event.  If this event remains on the current trajectory, it could rival our strongest El Niño events of recent memory (1997 in particular), with implications for both Southwest and global communities.

The recent above-average precipitation and below-average temperatures in Arizona and New Mexico are exactly the sort of patterns we expect to see under El Niño conditions. In the immediate future, we may see a return of some early season tropical storm activity, as we did with Hurricane Blanca in June. El Niño also points toward a possible delay in the start of the monsoon, which could actually extend the hotter and drier early portion of summer. We could also see a repeat of 2014’s above-average eastern Pacific tropical storm season, when conditions favorable to El Niño were thought to be driving increased late-season tropical storm activity in the Southwest.  And if El Niño persists into winter 2015-2016, particularly if it remains a moderate-to-strong event, we would likely see patterns of above-average precipitation in the Southwest (Fig. 5).


Image Source - NOAA Climate.gov

2015 El Niño Tracker

Friday, May 22, 2015

Originally published in the May 2015 CLIMAS SW Climate Outlook


El Niño continued for a third straight month, with no signs of weakening or dissipating. Forecasts keyed in on persistent sea surface temperature (SST) anomalies (Figs. 1–2), along with weakening trade winds, ongoing convective activity, and El Niño-related ocean-atmosphere coupling. If these conditions continue, we are likely to see the effects of a moderate El Niño event–or stronger if conditions continue to strengthen. Spring forecasts have a higher degree of uncertainty, owing to the so-called spring predictability barrier, a likely source of vacillations in recent forecasts. 

Image Source - Australian Bureau of Meteorology

Image Source - NOAA-National Climatic Data Center

Current forecasts offer a consistent and bullish forecast compared to last month, when they were integrating mixed signals regarding the strength of El Niño. On May 12, the Japan Meteorological Agency reversed course with an observation that strengthening El Niño conditions in the equatorial Pacific reflected an ongoing El Niño event that was likely to last through at least fall 2015. On May 12, the Australian Bureau of Meteorology upgraded its tracker to official El Niño status, identifying persistent SST anomalies, weak trade winds, and increasing ocean-atmospheric coupling serving as indicators this El Niño event was strong enough to extend into 2015. On May 14, the NOAA-Climate Prediction Center (CPC) extended its El Niño advisory with a 90 percent chance that El Niño will continue through summer 2015 and an 80 percent chance the event will last through 2015 (Fig. 3). The CPC pointed to positive SST anomalies, along with ongoing ocean-atmospheric coupling and dateline convection activity, as indicators of a weak to moderate El Niño event that will likely continue for most of 2015. On May 21, the International Research Institute for Climate and Society (IRI) and CPC forecasts confirmed we are in the midst of an El Niño event that appears to be strengthening, with the current forecast suggesting a moderate to strong El Niño event persisting into 2016. The North American multi-model ensemble shows a moderate event extending through the spring, with potential for a strong event by summer or early fall (Fig. 4).

Image Source - International Research Institute for Climate and Society

Image Source - NOAA-Climate Prediction Center

After a series of fits and starts, the pieces finally seem in place for the El Niño event forecasters expected to start last year. This is partially evidenced by the recent above-average precipitation and below-average temperatures in Arizona and New Mexico in late April and early May—exactly the sort of springtime weather we might expect to see if El Niño conditions were present and affecting our weather patterns. If the event persists into fall and winter 2015, and particularly if it remains a moderate to strong event, we will likely see patterns of above-average precipitation in the Southwest. There is also the possibility of a repeat of the 2014 tropical storm season, in which conditions favorable to El Niño were thought to have driven the increased tropical storm activity in the Southwest. 

Colorado River Delta: Pulse Flow - One Year Later

Wednesday, April 22, 2015

The Colorado River Delta hadn’t seen regularly flowing water in 50 years.  But one year ago the U.S. and Mexico came together to work on a project to move water down the empty riverbed.

On March 23, 2014 these countries released more than 100,000 acre-feet of water into the delta below the Morelos Dam.  This area is along the Colorado River on the U.S.-Mexico border. 

On May 15, 2014, the river finally met the sea.

They did this through a pulse flow.  A pulse flow can be thought of in terms of a surge of water or a spring flood.  It is designed to represent the natural flow that keeps the river healthy. 

Image/Data Source: Bureau of Reclamation

The amount of water allocated was less than 1 percent of the river’s average annual flow but even that small amount had lasting effects one year later.

On April 14, 2015 a panel was held at The University of Arizona to discuss the impacts of the pulse flow.  The panelists included Yamilett Carrillo, the executive director of the Delta Water Trust, Francisco Zamora Arroyo, the director of the Colorado River Delta Legacy Program at the Sonoran Institute and Karl Flessa a professor in the UA department of geosciences and a co-chief scientist with the Colorado River Delta Monitoring Program. 

Carrillo said after May 15, most river conditions returned to their previous state.  “But one key feature remained,” Carrillo said.   “There are patches of green areas where you can see the impacts of the pulse flow.” 

Flessa said that the eight-week flood helped germinate and establish cottonwoods and willows that will live up to 50 years, showing that even a small amount of water can drastically affect an environment.  He also said the existing vegetation certainly benefitted from the flow. 

However, the pulse flow didn’t have a lasting impact in all of the areas. 

"In some places the pulse flow did enormous amount of good work in establishing vegetation and sustaining that vegetation. In other parts of the river it didn’t really make that much of a difference," said Flessa.

Very little of the water stayed on the surface but a lot of it infiltrated into ground.

“It is not right to call this a loss because it really is a benefit for the vegetation that lives around here, the water gets to the vegetation by the roots,” said Flessa.

Researchers are trying to map out the river and identify the prime restoration sites.  Then future efforts will be aimed in the areas that responded positively to the water flow.  

NASA/Goddard Media Studios Video Highlighting the Pulse Flow

El Niño Tracker - April 2015

Friday, April 17, 2015

This was originally published in the April 2015 Southwest Climate Outlook


Strong signals in early 2014 stalled, delaying El Niño’s onset until last month, when ocean-atmosphere coupling and an additional Kelvin wave indicated more favorable conditions. Despite this late start, El Niño continued for a second consecutive month. Recent increases in sea surface temperature (SST) anomalies (Fig.1 - 2) and ongoing convective activity associated with El Niño-favorable conditions indicate we might be witnessing a two-year El Niño event. These forecasts rely on projections during a time of increasing uncertainty, and the so-called “spring predictability barrier” continues to make it difficult to anticipate how seasonal changes will help or hinder El Niño. 

Image Source - Australian Bureau of Meteorology

Image Source - NOAA-National Climatic Data Center

The most recent forecasts continue to offer mixed signals regarding El Niño, but are more bullish this spring than last year. On April 9, the NOAA-Climate Prediction Center (CPC) issued an El Niño advisory with a 70 percent chance that El Niño will continue through summer 2015 and more than a 60 percent chance the event would last through fall.  They pointed to the large Kelvin wave, along with ongoing ocean-atmospheric coupling, as an indication a weak El Niño event would linger, with potential for further development in the long term. On April 10, the Japan Meteorological Agency declared the El Niño event likely to have ended in winter 2015, with current conditions being ENSO-neutral, but also projected El Niño conditions could return by summer.  On April 14, the Australian Bureau of Meteorology upgraded their tracker to “alert” status (one below an official El Niño designation), with warming in the tropical Pacific, weak trade winds, and projected additional ocean warming listed as contributing factors. On April 16, the International Research Institute for Climate and Society (IRI) and CPC forecasts highlighted increasingly favorable oceanic and atmospheric conditions, with an 80 percent probability of El Niño extending from summer into fall, and a 70 percent probability of El Niño extending into next winter (Fig. 3).  The North American multi-model ensemble shows a weak event extending through the spring, with potential for a moderate or even strong event by summer or early fall (Fig. 4).

Image Source - International Research Institute for Climate and Society

Image Source - NOAA-Climate Prediction Center

This El Niño event continues to defy expectations, with some models indicating conditions are strengthening rather than weakening during the spring transition.  Forecasting or characterizing this event remains difficult given the lack of analog events in the historical record, and the complexity of this El Niño guarantees it will be of interest to climatologists for years to come. Seasonal forecasts continue to indicate an increased chance of above-average precipitation through much of the Southwest, likely tied to the presence of El Niño favorable conditions. Perhaps more interesting is the possibility of a repeat of 2014’s tropical storm season, when conditions favorable to El Niño were thought to have been driving increased storm activity in the Southwest.

Spring Signals the Start of Wildfire Season for the Southwest

Wednesday, April 15, 2015

A version of this post was also published in the April 2015 Southwest Climate Outlook


Flowers are blooming and trees have sprouted green leaves, signs that spring is in full swing across the Southwest and that, despite a verdant desert, wildfire season is upon us. The outlook for this wildfire season forecasts near-average wildfire activity for much of Arizona and New Mexico.

Several factors, including gradually increasing temperatures, a decreasing probability of precipitation, and increasing wind, create perfect climatological conditions for wildfire. From a climate perspective, spring is also a transition season, when the winter storm track lifts north and the sub-tropical high pressure system to the south starts to build north, both in response to an increasing sun angle and increased heating of the Northern Hemisphere. The retreat of the winter storm track and advancement of the sub-tropical ridge is generally not a clean transition, but a battle of cool and warm air masses that plays out over weeks, if not months. In this battle, the atmospheric pressure gradient tightens and wind speeds increase in response, creating conditions that can cause wildfires to grow quickly. In Arizona and New Mexico, hot, dry, and windy conditions are often the norm in late spring, and not surprisingly, this forms the heart of wildfire season for this part of the Southwest. 

Spring wildfire activity can be modulated by conditions from the previous winter, the previous summer, or even several years prior. Long-term drought conditions can stress and kill trees, increasing fire risk, but wet winters and strong monsoons can also drive increased fire risk. Fast-growing vegetation like grasses and annuals grow quickly during wet periods, then dry out and become fine fuels for subsequent wildfire seasons. 

The current wildfire outlook for the southwest notes that near-average wildfire activity is expected for much of Arizona and New Mexico, due largely to some improvements in drought conditions across the region, including above average precipitation last summer and into the early winter season. But this precipitation also spurred on new vegetation growth, increasing the risk of wildfires across southern Arizona this spring as this vegetation senesces and becomes flammable.  Fire managers will be watching these emergent conditions carefully, especially as dry and windy conditions create short-term windows of elevated fire risk.

Image Source - National Interagency Coordination Center

Image Source - National Interagency Coordination Center

El Niño Tracker - March 2015

Friday, March 20, 2015

Originally published Mar 19, 2015 in the CLIMAS Southwest Climate Outlook

After months of vacillating sea surface temperature (SST) anomalies, limited coordination between oceanic and atmospheric conditions favorable to El Niño formation, and ongoing confusion regarding the strength of the various diagnostic signals, El Niño has “officially” arrived in North America. This is late in the season to declare an El Niño, and the so-called spring predictability barrier makes it difficult to anticipate how seasonal changes, particularly westerly wind bursts, will help or hinder the ongoing conditions favorable to El Niño. This has been a strange season.  Strong signals in early 2014 stalled in summer and into fall, delaying the event’s onset until this month, when ocean-atmosphere coupling and an additional Kelvin wave again indicated more favorable conditions for an El Niño event.

The most recent forecasts offer mixed signals regarding El Niño. On Mar. 5, the NOAA-Climate Prediction Center (CPC) issued an El Niño advisory, maintaining a 50–60 percent probability of a weak El Niño event developing and extending through the summer. On Mar. 10, the Japan Meteorological Agency declared the El Niño event likely to have ended, with greater likelihood of a return to El Niño than ENSO neutral conditions in the summer. On Mar. 17, the Australian Bureau of Meteorology elevated its El Niño tracker from neutral back to watch status, noting the “unusual conditions” in the tropical Pacific, including warmer-than-average SST anomalies (Fig. 1-2). On Mar. 19, the International Research Institute for Climate and Society (IRI) and CPC reasserted a 50–60 percent probability of this El Niño event extending into summer 2015 (Fig. 3), similarly noting atypical (or even strange) conditions that have made characterizing this particular event difficult.  The North American multi-model ensemble shows a weak event extending into summer (Fig. 4), and corroborates the forecast discussion that suggests an increased possibility of a stronger El Niño signal extending into 2016.  While the models are bullish on the possibility of a moderate to strong event, this will depend on how ocean and atmospheric conditions progress from summer into fall. 

With a seemingly definitive El Niño declaration, we are finally out of “El Limbo”.  While forecasting or characterizing this event has been difficult for all involved, the complexity of this El Niño will be of interest to climatologists for years to come.  Looking forward, seasonal forecasts still indicate an increased chance of above-average precipitation through much of the Southwest for late winter and spring. Despite numerous storm events, we have yet to see widespread and sustained above-average winter precipitation in the Southwest, which would help considerably in mitigating longer-term drought conditions.

Image Source - Australian Bureau of Meteorology

Image Source - NOAA-National Climatic Data Center

Image Source - International Research Institute for Climate and Society

Image Source - NOAA-Climate Prediction Center

Chris Guiterman - 2014 CLIMAS Climate & Society Graduate Fellow

Thursday, March 12, 2015

From the very beginning, Chris Guiterman just wanted an opportunity to expand his collaboration with the Navajo Forestry Department, and to demonstrate what he could do to help them. 

Guiterman is a 2014 recipient of the Climate Assessment for the Southwest (CLIMAS) Climate & Society Graduate Fellows Program. He is currently a PhD student at the University of Arizona, School of Natural Resources and the Environment, working in the Laboratory of Tree-Ring Research.

He used the CLIMAS fellowship to jumpstart a project that he had been struggling to fund.

Tribal nations across the Southwest are increasingly at risk of climate change impacts on the landscape, and because many of these nations rely on the ecosystem services of healthy forests, the risks are intensified. 

“Tasked with managing over 5 million acres of forests and woodlands, the Navajo Forestry Department has identified the need to assess sensitivities of their forests to drought and climate change,” according to the abstract of Guiterman’s research project. Guiterman worked with the NFD foresters to address their needs by quantifying the climatic drivers of forest growth in the Chuska Mountains.

Previously, Guiterman worked with the NFD on another project for a couple of years, and he and his NFD collaborators had a series of discussions about what the next steps could be. Guiterman basically told the NFD, “you can see what I can do…what do you need? And what can I do for you?”

Guiterman said the project spawned from that initial conversation, and the NFD essentially asked him the research questions. 

They wanted to know how vulnerable their forests are to climate change, what the long-term productivity of their forests would look like, and the overall age of the forests.

“I was really excited to be able to contribute and to be able to give them some knowledge that they want, and that I actually have the skills and capacity to do,” Guiterman said. “I understand what it is like to be a forest manager from my background, so I know how valuable this information is.” 

This was a win-win for both the NFD and Guiterman.  He found the research compelling because it was at the core of what he does as a scientist, and it was also directly beneficial to a group who needed this information and analysis, and who had plans to use it.  

When Guiterman approached CLIMAS with this study, he knew that his ambitions were bigger than the five thousand dollar budget CLIMAS allowed.  But he didn’t care. 

“I told the Navajo foresters I could do something when they asked me a question,” Guiterman said. “I told them I could help answer it and I just wanted a start to show them that we could go in the woods, we could all core trees, I could bring back data and show them x,y and z to help answer their questions.”

Throughout this project, Guiterman learned a lot about what it means to work on a Native American reservation.  Because the tribal government functions differently than he is used to, he had to learn as he went along.  “I think I jumped a few hurdles before I ever knew they existed and then I backed up,” Guiterman said.  “They were willing to work with me, be patient and understanding.”

Although learning the rules and regulations was difficult at first for Guiterman, it was also very rewarding. “Trust and credibility in a relationship are paramount to doing the kind of work that I want to keep doing and what this project emphasizes,” said Guiterman.

Guiterman worked in the field with two men from the NFD, who had been there for at least 20 years, and they helped core most of the trees. The fieldwork was complete in June of 2014.  They visited 7 plots, cored 111 trees and took 222 cores back to the lab. 

“I learned a lot just by being around them in the woods, asking what they saw and what they thought,” Guiterman said.

One thing Guiterman wasn’t expecting was how much they taught him about navigating the road network in the area.  “There are roads everywhere and there are few markers, some of them aren’t even on the map,” Guiterman said.  “Local knowledge is so key when you are in the forest landscape.”

This project took the men out to plots in the middle of the forest, so Guiterman usually gave the Navajo foresters the plot locations and he would follow behind so he wouldn’t get lost. 

“We would be driving along and we would just turn off the road into what to me looked like a meadow and drive on up,” Gutierman said.  “A couple of times they would disappear and I would have no idea where they were going because I didn’t see the road there.”

As Guiterman followed, a road would appear. Somehow, the foresters knew it would be there.

Guiterman was able to begin his research with the CLIMAS fellowship, and has subsequently received a fellowship from The Environmental Protection Agency (EPA Star) and a grant from the Bureau of Indian Affairs (BIA).  With this extra funding, Guiterman has been able to make this project part of his dissertation, which he intends to finish in August of 2016. 

Guiterman is also excited to finally be a part of CLIMAS.  He has always admired their work and with this fellowship, not only did he get to do this project, but he also joined a community of people that he wants to work with.

 

Rebecca Lybrand - 2014 CLIMAS Climate & Society Graduate Fellow

Wednesday, March 11, 2015

To Rebecca Lybrand, calling soil “dirt” is simplistic and diminishes its importance to plants, animals, and human beings.  So why is soil, the foundation of life, constantly being referred to as “dirt?”  Rebecca began this line of thinking in college, and this spark of curiosity turned a simple question into a career. 

Rebecca is now a soil scientist at The University of Arizona.  She received her Ph.D. from The University of Arizona’s Department of Soil, Water and Environmental Science (SWES) in 2014. She is also a recipient of the 2014 Climate Assessment for the Southwest (CLIMAS) Climate & Society Graduate Fellowship. 

Rebecca’s CLIMAS project centered on creating two short films that documented her research across the Santa Catalina Mountains in Arizona. These films showcase four of her field sites, which span over 4000 feet of elevation gain. The sites differ in temperature, precipitation, and vegetation, all of which have remarkable impacts on the characteristics of these soils. 

The visuals for both films are the same, but the scripts change to present the science message in two different contexts. One uses a lively, first person perspective that relays a scientific story, using Rebecca’s personal experience to frame the film.  The other is in third person, and presents a formal video delivering a more scientific message along the lines of what you might see in a science documentary. The main objective of this project is to survey students and to evaluate the effectiveness of formal and informal communication techniques.

Rebecca had been interested in doing this project for quite some time.  The year before she was a CLIMAS C&S graduate fellow, she was part of the Carson Scholars program, where she learned more about how to communicate science effectively. As a Carson Scholars Fellow, Rebecca saw the potential for making a soils video and even connected with Dr. Jay Hmielowski, an assistant professor specializing in Environmental Communication, who was willing to collaborate on the project. However, at the time, Rebecca was a graduate student and did not have a lot of free time or extra funding available to make the video happen.

In the back of Rebecca’s mind she knew that she wanted to make this video. She went out in the field to shoot footage and she even began to make connections with a local media and communications expert, all before learning about the CLIMAS fellowship. 

“Seeing the CLIMAS announcement and completing the proposal process is what solidified it,” said Rebecca.  “The CLIMAS fellowship made this outreach project happen.”

Rebecca didn’t have much experience with shooting footage or editing video prior to working on this project. Her inspiration actually came from mountain biking. Both she and her fiancé mountain bike, and enjoy using a GoPro camera to film their adventures on the trails. Moreover, they are avid fans of attention-grabbing, professionally produced mountain biking documentaries.

 “I always thought that the videos were really engaging and even people who don’t mountain bike enjoy watching them,” said Rebecca.  “I kept thinking, this is the way to present science, in a fun and interactive way.”

Because Rebecca had little experience with making a film, she reached out to Shipherd Reed, the Marketing and Communications Manager at the UA Flandrau Science Center. Shipherd helped Rebecca along the way with things such as how to capture footage and how to navigate Final Cut Pro.  Rebecca says he was very willing to help and extremely patient. 

Because Rebecca had never edited video before, her main challenge was that everything took much longer than she anticipated.  She had captured hours of video and then watched every second of it, taking notes along the way. 

“In my proposal I put together my nicely framed timeline, which was completely unrealistic,” said Rebecca.  “Every step took hours, days or even months longer than I had planned on, but it was worth it.”

Difficulties aside, Rebecca made great memories putting this film together.  On the longest day of shooting, Rebecca and her fiancé were on the road to a field site before the sun rose and were hiking back from another field site as the sun went down.

“We reflect back on that day and laugh. I know that we were both exhausted by the time we got home, but it was a really fun and exciting day,” said Rebecca.  “We also saw a Gila monster, so that was an added reward because I love reptiles.”

Now that both videos are complete, Rebecca has teamed up with her collaborator, Dr. Hmielowski, to write and carry out student pre-tests and surveys to test the effectiveness of the contrasting narrative strategies.  Rebecca hopes to present the study at a science communication conference with the ultimate goal of publishing her findings to reach a larger audience. 

Rebecca is now working on her Postdoc with Dr. Rachel Gallery’s soil microbial ecology research group. She is looking at how soils and topography are impacting soil microbes across pine beetle- and fire-disturbed environments in Colorado. Rebecca intends to continue working as a soil scientist and plans to maintain her science outreach work in the community. She knows that having this readily available video and the skills required to produce more videos will help her in the future. 

“Everyone is always interested in the different types of outreach work that you do and in knowing that you are able to communicate to interdisciplinary teams of scientists and the public,” said Rebecca.  “Having this real concrete visual representation of my research is a great product.”

Ling-Yee Huang - 2014 CLIMAS Climate & Society Graduate Fellow

Tuesday, March 10, 2015

When Ling-Yee Huang received the Climate Assessment for the Southwest (CLIMAS) Climate & Society Graduate Fellowship a year ago, she proposed to create a climate science curriculum for law schools.  Little did she know, she would actually be teaching her own class on climate science curriculum for lawyers, at the James A. College of Law at The University of Arizona.

Huang is currently a M.S. student in the School of Natural Resources and the Environment (SNRE) at the University of Arizona, as well as a researcher at the Water Resources Research Center (WRRC).  Previously, she earned a J.D. from the University of Florida Levin College of Law and a bachelor’s degree in biology from Rice University.

Before coming to UA, Huang worked as a policy analyst for the Center for Progressive Reform in Washington, D.C.  She provided legal analysis regarding the Clean Water Act and restoration of the Chesapeake Bay, and she developed legal frameworks for climate change adaptation and protecting ecosystem services.

“I have always really liked the idea of combining science and decision making,” said Huang.  “I started grad school having worked in the decision and policy making field for a couple of years and in that experience I felt that there was a real lack of understanding of science.”

Huang said when she learned about the CLIMAS fellowship, she realized it captured her dual interests in both science and policy perfectly. The curriculum and her final project were ideas she had been contemplating for a long time. 

“I found it the perfect fit,” said Huang. 

Huang’s CLIMAS Fellows project is Achieving Scientific Literacy in the Classroom: A Climate Science and Law Curriculum

Huang said she realizes there was a lot of interest in doing science literacy education in the legal field, but there weren’t many examples of exactly what she was trying to do.  For example, there are classes on climate change law, where students spend a few short lectures going over climate processes, but the focus is on the legal aspect of things, which makes sense in a law school.

Huang’s curriculum is different in that it orients students into thinking a certain way and towards being able to ask informed questions.

“I am not expecting them to be scientists but at least they are able to think critically about data that they are presented,” said Huang.

When Huang began, she had an ambitious curriculum. “I wanted to talk about air quality and water quality and climate process and how science works,” said Huang. “I had all of these topics that I wanted to cover in 8 weeks but when I presented it to one of the law professors who was helping me, she told me I really needed to scale back my ambitions.” 

The professor told her it was enough to just try to teach people about graphs.

With Huang’s final curriculum, students will learn how and where science and law interact, they will understand the basic scientific process, they will develop basic scientific literacy skills, they will apply the skills in a legal context, and they will learn the basics of climate science law. And she will do this all in 8 weeks!

“Trying to understand what I wanted to teach and what could realistically be taught in the constraints of the semester that was given to me was hard,” said Huang.  “I feel like there is so much information that could be useful for law students to know, but then being realistic about what was the most important was probably the most challenging for me.”

Difficulties aside, Huang created a curriculum that not only can be applied to law schools around the country but will definitely be in use in at the James A. College of Law.  Huang will be teaching Integrating Science and the Law in Practice (LAW698O), beginning March 3, 2015. 

Huang entered grad school with the idea that she wanted to have one foot each in the science and policy worlds. She wanted to figure out how to bridge communication gaps so that policies, however they turned out, are better informed by scientific research.

Huang said she wouldn’t have come up with this curriculum or put the work into it without this fellowship.

“I think UA is really fortunate to have an organization that is interested in funding this kind of policy, science type of work,” said Huang, referring to CLIMAS.  “Very often in academia, we get into our one discipline and we go, go, and go without looking across the horizon to see what is out there.”

Sarah Truebe - 2014 CLIMAS Climate & Society Graduate Fellow

Monday, March 9, 2015

Sarah Truebe has always been a caver.  She grew up thinking the only things people should take from caves are photographs, but as she began her career as a paleoclimate scientist, she realized that scientists often take a lot more than photographs.

A stalagmite is a cylindrical mineral deposit, formed over hundreds or thousands of years on the floor of a cave, making them utterly non-renewable on human timescales.  Stalagmites contain valuable paleoclimate data; however, most of the time getting this information means permanently removing the stalagmite from the cave. 

“As the popularity of stalagmite paleoclimate science grows, development of sustainable sampling methods for these nonrenewable resources is necessary to balance the needs of science and cave conservation,” Truebe said. 

Truebe is a PhD candidate in the Department of Geosciences at the University of Arizona and is also a 2014 recipient of the Climate Assessment for the Southwest (CLIMAS) Climate & Society Graduate Fellows Program. She used this opportunity to collect information on different stalagmite sampling methods, with the intention of developing best practice recommendations for extraction. 

Truebe said the fellowship was very timely.  “Over the last 3 years of my PhD I have been thinking more and more that I want to be doing is science that is not only directly relevant to stakeholders, but is actually something that is engaged with stakeholders,” Truebe said.

She surveyed scientists on the different methods they currently or ideally want to use to extract climate information from the stalagmites. She asked stakeholders about which of the methods make the most sense to use, given the many other uses for caves, including tourism, education, recreation, habitat for many organisms, and so forth.

There were a few popular methods mentioned by scientists

  • The stalagmites can be cored, which leaves the majority of the structure intact; 
  • Broken or vandalized stalagmites can be permanently removed and analyzed;
  • Intact stalagmites can be temporarily removed and analyzed, and then repaired and replaced, or they can also be permanently removed and archived after climate information has been extracted.

While there are a few more techniques, these are the most popular methods. 

 “I had already done all of the scientist surveys before I heard about the fellowship and so I said this is a really cool project and there is a lot of potentially interesting information here, so how can we really do a great job on the stakeholder side of things too?” Truebe said.  “That was my intention in applying for the fellowship.”

The first survey covered which methods were being used or favored by these scientists. Truebe contacted 70 paleoclimate labs and received 45 responses to the survey, from 19 different countries.

The results showed that all of these scientists were removing the stalagmites from the cave permanently for sampling.  While less than 25 percent were using other techniques, the main method was permanent removal. 

From this study, Truebe found that one third of the scientists were not using their ideal or preferred method.  She also found they had awareness of the need or importance of conservation, but that there is not time, incentive or funding to do anything differently. 

A second survey was targeted at stakeholders, a group that included cave managers, state and federal agencies and recreational cavers.  There were 110 competed surveys with this group and while surveys were submitted from eight different counties, most came from the U.S.

These results for this survey were quite different compared to the scientist’s survey.  Permanent removal was a much less favored technique, while less-destructive coring was preferred. However, Sarah mentioned that coring isn’t always possible, depending on the geometry of the stalagmite.

After completing the surveys, Sarah built a framework that will give managers and scientists a place to start when wanting to sample in a more conservation-friendly way.  Along with this framework, Truebe will be writing a journal article for The National Speleogical Society and for the Journal of Cave and Karst Studies.

While Truebe thinks that these outputs are necessary, she felt she needed something else to really get the conversation about new sampling techniques started.  So she is also planning on holding two workshops, one on archiving that will primarily reach scientists and the other on developing new methods that will engage with interested stakeholders. 

Truebe said she was a bit concerned going into the project.  “Removing stalagmites is a very destructive process,” Truebe said. “So I was a bit nervous to send this survey out to the world wide caving community and say, “hey, there is this issue that you may or may not be aware of, what do you think about it?’”

 She was also worried to send it to scientists, who might not want a spotlight put on their sampling methods, because many know that sampling is already at odds to cave conservation.

But she was pleasantly surprised that people weren’t defensive or resistant to having a discussion, and most were receptive to the idea of shifting to a more conservation-oriented perspective, and were interested in how to do sampling better.  They were eager to find a compromise between what the scientists want and need to do for a robust analysis and what is good for the cave, long-term. 

Truebe is excited to see how this affects the future of caving and cave paleoclimate science.

“Now we can actually engage with the uncomfortable feelings that I have been having about this type of work and that other scientists expressed to me in the survey,” Truebe said.  “It is okay because we can study this and we can move forward.” 

Truebe said the fellowship made this idea that she had been thinking about for a while, more real. 

“I think that it has helped a lot, mainly because it has given much more credibility to the project, which until I received the fellowship was really just a thought experiment, or something like that,” said Truebe.  “Because the project is credible as is, but it was nice to be able to say ‘hey, I’m not the only one who thinks so.’”

El Niño Tracker - Southwest Climate Outlook February 2015

Friday, February 20, 2015

Originally published in the Feb 2015 CLIMAS Southwest Climate Outlook

2014-15 El Niño Tracker

A definitive 2014–2015 El Niño forecast remains elusive. Weak El Niño conditions have continued in 2015, but recent backsliding in SST anomalies (Fig. 1), especially in the Niño 1-2 regions (Fig. 2), along with the ongoing lack of coordination between atmospheric and oceanic conditions, give little confidence that the 2014–2015 event will be characterized as anything more than a weak El Niño.

Image Source - Australian Bureau of Meteorology

Image Source - NOAA-National Climatic Data Center

The most recent forecasts dialed back the probabilities for El Niño this winter and spring, and hinted we could swing to ENSO-neutral by late spring. On Feb. 5, the NOAA-Climate Prediction Center (CPC) issued another El Niño Watch, maintaining a 50–60 percent probability of an El Niño event, most likely a weak event extending into late winter or early spring. On Feb. 10, the Japan Meteorological Agency continued its assessment that El Niño conditions had been present in the equatorial Pacific for multiple months. They noted uncertainty as to the length or intensity of an El Niño event, with emphasis on a weak event that would transition to ENSO-neutral by early spring. On Feb. 17, the Australian Bureau of Meteorology kept its El Niño tracker status at neutral, given the fade in SST anomalies and lack of clear atmospheric signal. On Feb. 19, the International Research Institute for Climate and Society (IRI) and CPC reasserted a 50–60 percent probability of an El Niño event (Fig. 3).  Given the declining SST anomalies and lack of clear atmospheric signal, they characterized this event as a “borderline El Niño” that would last through early spring 2015. The North American multi-model ensemble shows a weak event that extends into summer (Fig. 4). This graph highlights the possibility of a continuation of a stronger El Niño signal into 2015 (a possibility that was discussed in the IRI-CPC forecast event), depending on how ocean and atmospheric conditions progress from summer into fall.  The dynamical models currently favor a resurgence of El Niño conditions, while the statistical models suggest an ENSO-neutral state.

As with last month, we remain in “El Limbo” with seasonal forecasts still indicating an increased chance of above-average precipitation across the Southwest for winter and early spring. These forecasts are linked to the projected influence of El Niño conditions, but impacts associated with weak El Niño events are less certain than those associated with moderate or strong events (past weak events have brought both dry and wet conditions to the Southwest during the winter). A number of storm events have moved through the Southwest in late 2014 and early 2015, but conditions have not converged to produce widespread above-average precipitation over an extended period of time.  For this El Niño event to be of some utility in mitigating longer-term drought conditions, we would hope to see this convergence this winter into spring, with more widespread and sustained precipitation events.

Image Source - International Research Institute for Climate and Society

Image Source - NOAA-Climate Prediction Center

Notes from an Applied Climatologist: East/West Cold/Hot Dichotomy Q&A

Friday, February 20, 2015

Originally published in Feb 2015 CLIMAS Southwest Climate Outlook:


Why has it been so cold on the East Coast, and so warm in the Southwest?  Where does this fit into climatic patterns?  And is this extraordinary or just variability?

The weather pattern across the U.S. has been pretty extreme over the past weeks, with record cold and snow across the East and record to near-record warmth in the West. Why is the country so divided? In short, a wavy jet stream is to blame (Fig. 1). This high-altitude stream of fast-moving winds has been carving a circuitous path around the globe for much of the winter. The path of the winter mid-latitude jet stream around the globe (in both hemispheres) can give a good indication of where storms are tracking and where warm and cold spots at the surface are emerging. If the jet stream gets stuck in any position, then places getting storms can continue to see a parade of storms, while warm and dry places stay warm and dry. 

Image Source - NOAA-Earth Systems Resarch Laboratory (ESRL)

This winter, the mid-latitude jet stream in the Northern Hemisphere has been very wavy, or meridional [1], with ridges—large-scale bulges—to the north and troughs to the south. Ridges are associated with warm and dry conditions, while troughs are associated with cold and possibly snowy or rainy conditions. Over the past several weeks, this warm West/cold East pattern has dominated, with a persistent ridge of high pressure across the West and a very cold trough across the East (Fig. 2).  Last year, similar conditions drove California and much of the Southwest deeper into drought and unleashed record-setting cold [2] in the eastern U.S. This year, these conditions have broken down on occasion, allowing for storms to bring some precipitation to the West and for the East to warm up for brief periods.

Researchers are trying to determine why this dichotomous pattern has emerged and persisted over the past couple of years. Some climate scientists propose that a warming Artic and declining sea ice [3] are contributing to an increasing frequency of wavy and stuck jet stream events. Other scientists argue that warming water [4] in the tropics and shifts in tropical convection are at play in impacting the winter jet stream pattern. This winter appears to be a complex interaction of many different factors [5] and will be studied in more detail over the coming year to see how it fits into these active areas of research.

Image Source - NOAA-ESRL & Climate.gov

Additional Resources

  1. Meridional: In meteorology, a flow, average, or functional variation taken in a direction that is parallel to a line of longitude; along a meridian; northerly or southerly; as opposed to zonal. 
  2. U.S. temperature extremes and the polar jet stream
  3. Evidence for a wavier jet stream in response to rapid Arctic warming
  4. Record-breaking winters and global climate change
  5. Synoptic Discussion - January 2015

2015 CLIMAS Climate & Society Graduate Fellows

Thursday, February 12, 2015

The Climate & Society Graduate Fellows Program supports University of Arizona graduate students whose work connects climate research and decision making. Fellows receive $5,000 and guidance from members of the CLIMAS research team (Climate Assessment for the Southwest) for one year. The program’s main objective is to train a group of students to cross the traditional boundaries of academic research into use-inspired science and applied research. While CLIMAS research generally occurs in the Southwest U.S., the Fellows program allows students to work anywhere in the world.

Fellows’ projects may follow two tracks. Students who want to conduct collaborative research may use their funding for use-inspired projects. Students who have conducted climate research and want to communicate their findings to audiences outside of academia may use their funding for outreach. Fellows may also use their funding for a combination of the two tracks.

The Climate & Society Graduate Fellows Program helps students address the world’s climate-related problems by funding projects that engage people outside of the university.

The 2015 Climate Assessment for the Southwest (CLIMAS) Climate & Society Graduate Fellows are:


Christina Greene

Abstract: A history of prolonged droughts has long challenged the food system in the Southwest, and these challenges will become steeper under a future of climate change. This project seeks to better understand the vulnerability of the food system to drought by focusing on the impacts of the California drought on farmworkers. By identifying the needs of farmworkers during drought and evaluating the distribution of drought relief boxes through community food banks, this research seeks to connect the environmental and social dimensions of drought, labor, and food insecurity.


Eric Magrane

Abstract: As a CLIMAS fellow, Eric Magrane will design and teach a community course for the University of Arizona Poetry Center called “Climate Change and Poetry.” Climate change is both a scientific and a social issue. It is a threat to life on Earth as we know it as well as an opportunity for social change and environmental justice. A growing body of poetry addresses climate change, and this course will use poems as boundary objects to both communicate climate change and to examine its different frames or narratives. It will explore what role the imaginative and emotional resonances of poetry might have in the way we think about adaptation and mitigation. 


Valerie Rountree

Abstract: In March 2015, the City of Tucson Office of the Mayor will hold a half-day summit on Energy and the Economy with policy makers and business owners in Tucson to discuss the economic opportunities associated with increasing energy and the use of renewable energy. The purpose of Valerie’s CLIMAS project is to enhance the summit and evaluate its success in engaging participants and initiating action on energy efficiency and renewable energy in the private sector.  The project will include three parts: first, a pre-summit survey of prospective attendees will be administered to get baseline data regarding participants’ opinions and knowledge of energy efficiency.  The results of the survey will also be used to tailor the content of the summit to participants’ interests.  Second, a post-summit survey of attendees will be administered to evaluate the impacts of the summit on attendee opinions, knowledge and perceptions.  And third, follow-up interviews will complement surveys to evaluate whether participants plan to implement energy efficiency measures.  The results of this project will be used by partners in the Mayor’s Office to enhance the 2015 Summit and improve summits in future years.


Bhuwan Thapa

Abstract: Nepal’s water resources and agriculture sectors are one of hard hit sectors by climate variability and change. There are about 25,000 irrigation Systems which are managed by farmers and which irrigate about 25 percent of total irrigated area in Nepal. Though Farmer-managed irrigation system (FMIS) is considered a robust system, it is facing increasing stresses from climatic and non-climatic elements including competing water demands, frequent infrastructure damage from flooding and landslides, degraded water quality, and poor governance. My study will conduct use-inspired research on adaptation strategies of FMIS in order to strengthen their management capacity. As a part of the project, I will conduct i) participatory assessment of biophysical and social vulnerabilities of the FMIS to climatic stresses; and ii) support the irrigation managers with development of appropriate adaptation strategies.

El Niño Tracker - January 2015

Friday, January 23, 2015

Originally published in the January 2015 Southwest Climate Outlook (SWCO)

Just when it looked like we were getting a more definitive answer regarding El Niño, ongoing lack of cooperation on the part of the atmosphere continues to muddy forecasts moving into 2015. Sea surface temperatures (SSTs) remain elevated across much of the equatorial Pacific Ocean (Fig. 1), and while temperature anomalies in the Niño 3.4 region are within the range of a weak El Niño event, they have declined in the past month (Fig. 2). It is a common refrain in forecast bulletins that a lack of coupling between ocean and atmosphere is responsible for decreased confidence in an El Niño event this winter. Additionally, a lack of temperature gradient along the equatorial Pacific and little in the way of El Niño wind patterns further reduce confidence that a stronger event is on the horizon.

Source: Australian Bureau of Meteorology

Source: NOAA-National Climatic Data Center

The most recent forecasts remain in a cautious holding pattern, pending the emergence of a more decisive signal. On Jan. 8, the NOAA-Climate Prediction Center (CPC) issued another El Niño Watch, assigning a 50 to 60 percent probability that an El Niño would form in the next two months, with forecaster consensus that this would be a weak event extending into late winter or early spring. On Jan. 9, the Japan Meteorological Agency continued its assessment that El Niño conditions had been present in the equatorial Pacific for multiple months but noted uncertainty as to the length or intensity of an El Niño event, with emphasis on a weak event that would transition to ENSO-neutral by early spring. On Jan. 15, the International Research Institute for Climate and Society (IRI) and CPC scaled back the probability of an El Niño formation to approximately 60 percent (Fig. 3) but indicated SST anomalies were sufficient enough to suggest a weak El Niño event was likely underway and would last through spring 2015. On Jan. 20, the Australian Bureau of Meteorology actually shifted its El Niño tracker status to neutral, given the fade in SST anomalies and lack of clear atmospheric signal. The North American multi-model ensemble shows a weak event that extends into summer (Fig. 4). 

Source: International Research Institute for Climate and Society

Source: NOAA-Climate Prediction Center

Vacillations in forecast percentages prompted the forecast community to describe current conditions as “El Limbo.” Despite lack of official status, El Niño-like conditions may already be driving winter patterns, and seasonal precipitation forecasts indicate an enhanced chance for above-average precipitation this winter across the Southwest, although confidence in this forecast is partially contingent on the strength of these El Niño conditions. Impacts associated with weak El Niño events are generally less certain than those of a moderate or strong event, with past weak events bringing both dry and wet conditions to the Southwest U.S. during the winter. Ultimately, the above-average tropical storm season and the humidity that remained in the region may be indicative of the effect of El Niño-like conditions, even in the absence of a formal designation, and give some idea that the regional patterns have shifted in favor of El Niño formation.

El Niño Tracker Update - December 2014

Friday, December 19, 2014

From the Dec 18, 2014 - Southwest Climate Outlook - 

We are still waiting for a decisive signal, but conditions indicate we are near, or possibly already into, at least a weak El Niño event. Sea surface temperatures (SSTs) are elevated across the equatorial Pacific Ocean (Fig. 1), and the measurements in the Niño 3.4 region are indicative of El Niño having already started (Fig. 2).

There remains a distinct lack of cooperation on the part of the atmosphere. This lack of coupling between ocean and atmosphere (demonstrated by near-normal wind and rainfall anomalies), along with a lack of temperature gradient along the equatorial Pacific and little in the way of El Niño wind patterns, means that while we are likely already experiencing El Niño-like conditions in the Southwest (e.g. some of the recent wet weather), it may be a little longer before a formal declaration occurs, even if retroactively.  

On Dec. 4, the NOAA-Climate Prediction Center (CPC) issued another El Niño Watch, with a 65 percent probability of a weak El Niño event occurring.  Anomalous SSTs alone were probably enough to suggest a weak El Niño event, but the lack of atmospheric coupling kept the current assessment at ENSO-neutral.  On Dec. 10, the Japan Meteorological Agency declared that an El Niño started in late summer and that it would continue through early 2015. This was based on favorable El Niño conditions and elevated SSTs, even while other more robust criteria were not yet met. On Dec. 16, the Australian Government’s Bureau of Meteorology maintained its El Niño tracker status at El Niño Alert status, despite a lack of atmospheric conditions to complement the anomalous SSTs. That outlook assigned a 70 percent probability of a weak El Niño event developing in winter 2014–2015. The Dec. 18 International Research Institute for Climate and Society (IRI) and CPC upped the probability of El Niño conditions developing to more than 80 percent in the next three months and more than 70 percent through spring and into summer (Fig. 3).

The North American multi-model ensemble shows a weak event that extends well into spring (Fig. 4). The extended period of above-average SSTs appears to be increasing confidence in the formation of El Niño this winter into spring.

Seasonal precipitation forecasts still indicate an enhanced chance of above-average precipitation over the upcoming winter, but confidence in this forecast is partially contingent on the strength of the emerging El Niño event. The impacts associated with weak El Niño events are generally less certain than those of a moderate or strong event, with past weak events bringing both dry and wet conditions to the Southwest U.S. during the winter. Ultimately, the above-average tropical storm season and the humidity that has remained in the region may be indicative of the effect of El Niño-like conditions, and we may be seeing the emergent effects of El Niño impacts on the climate of the Southwest, despite the absence of a formal definition identifying the start of a bounded El Niño event.

El Niño Tracker Update - Late November 2014

Friday, November 21, 2014

From the Nov 20, 2014 Southwest Climate Outlook

The long-awaited El Niño event projected to develop during winter 2014 – 2015 has yet to send a decisive signal regarding an official start, but a number of factors have increased forecasters’ confidence that one will emerge. The strength of this event still remains in question, however with the most likely projection still centering on a weak or weak to moderate event.

On Nov 6, the NOAA-Climate Prediction Center (CPC) issued an El Niño Watch, assigning a 58 percent probability that an El Niño would form and that it most likely would be weak. This forecast was based on a slight increase of sea surface temperatures (SSTs) across the eastern equatorial Pacific, linked to the contribution of the Kelvin wave (discussed last month), which helped warm SSTs in the eastern Pacific.  The CPC also reported the “ongoing lack of clear atmosphere-ocean coupling” (discussed in our previous Southwest Climate Podcasts) reduced confidence in the forecast.  On Nov 18, the Australian Government Board of Meteorology increased its El Niño tracker status from El Niño Watch to El Niño Alert, with a 70 percent probability of an El Niño developing in winter 2014–2015.  This outlook was based on a recent surge in above-average temperatures in the tropical Pacific Ocean (Fig. 1) and the Southern Oscillation Index (Fig. 2), which exceeded the El Niño threshold for the past three months, despite a lack of complete cooperation on the part of atmospheric conditions.

The Nov. 20 International Research Institute for Climate and Society (IRI) and CPC forecast reiterated these points, as the SSTs have exceeded the threshold for weak El Niño conditions, even while some of the atmospheric variables have yet to point towards an El Niño event. The mid-November forecast subsequently upped the probability of El Niño conditions developing to 75 percent (Fig. 3), and the North American multi-model ensemble shows a weak to moderate event peaking in mid to late winter and extending into the spring (Fig. 4).  

The strength of the event, if and when it forms, will matter. The impacts associated with weak El Niño events are generally less certain than those of a moderate or strong event, with past weak events bringing both dry and wet conditions to the Southwest U.S. during the winter. Seasonal precipitation forecasts still indicate an enhanced chance of above-average precipitation over the upcoming winter, but confidence in this forecast is partially contingent on the strength of the emerging El Niño event. It should also be noted that the signal for the Pacific Decadal Oscillation (PDO) has moved into a positive phase, which bodes well for increased precipitation this winter, especially since the El Niño-Southern Oscillation (ENSO) and PDO signals have the potential to enhance, rather than work against, the other.

2014 Pacific Hurricane Season Recap - Focused on the Southwest

Friday, November 21, 2014

From the Nov 20, 2014 Southwest Climate Outlook

The 2014 Pacific hurricane season was the most active season on record since 1992, with 20 named storms (Fig. 1). Fourteen of those storms developed into hurricanes, including eight major hurricanes (category 3 or greater), also breaking a record held since 1992. This meets or exceeds the high end of the NOAA-Climate Prediction Center (CPC) seasonal forecast (May 22), which predicted 14 to 20 named storms, seven to 11 hurricanes, and three to six major hurricanes. The Pacific hurricane forecast was tied to the ongoing El Niño forecast discussion, as conditions linked to the formation of an El Niño event (e.g., decreased wind shear in the tropical Pacific) also favored increased hurricane frequency and intensity in the Pacific region, and it is safe to say this season did not disappoint.  Conversely, the Atlantic hurricane season was relatively quiet, with eight named storms, six of which became hurricanes, including two major ones.  This was also in line with NOAA-CPC projections of seven to 12 named storms, three to six hurricanes, and up to two major hurricanes.

Seasonal Summary and Impact on the Southwest

The season started off strong and early with Hurricane Amanda on May 24 and continued with a number of early season tropical storms and hurricanes. A few early seasons storms, including Amanda, affected portions of Mexico but largely avoided the Southwest U.S. Most followed the typical early season pattern of staying out in the Pacific Ocean.  Notably, Hurricanes Iselle and Julio headed towards the Hawaiian Islands in late July and early August, with only Iselle actually making landfall.  As the season progressed, later season storms followed the expected pattern of recurving back into the Pacific Coast (see additional resources), and a number of major hurricanes, notably Marie, Norbert (with an assist from Atlantic Hurricane Dolly), Odile, and Simon, veered into the Pacific coast and brought considerable moisture into the Southwest. These incursions of rainfall made substantial contributions to the region’s overall monsoon totals; without them, the Southwest likely would be looking at a very different monsoon picture (i.e., below-average precipitation), particularly in September.

Specific Impacts and Looking Forward

In the Southwest, we are accustomed to the seasonal threat of flooding associated with intense monsoon precipitation, but these storms are generally highly variable spatially and relatively short. Hurricane Odile, as it lumbered into the Southwest, presented a unique threat; it had the potential for widespread flooding over a large area and over a number of days. In a worst case scenario, it could have moved slowly across the Tucson region, and dumped six or more inches of rain across the city and Pima County, not to mention additional flood potential from mountain runoff.  

This scenario posed unique challenges for emergency managers tasked with planning and preparing without sensationalizing or inciting fear in the community. Forecasters faced a related challenge of accurately characterizing a storm for which there was limited data available as it moved over data-poor regions of Mexico, knowing that the results of their forecast would be used to make widespread decisions that could prove costly if wrong. The lack of quality data, combined with apprehension about underestimating the threat of Odile, likely contributed to elevated predictions and certain planning decisions. 

Ultimately, Odile swung south of its predicted path by about 70 miles, leading to substantial rain events and considerable flooding in the southeastern corner of Arizona and across portions of southern New Mexico (Fig. 1). Tucson may have avoided the worst-case scenario in terms of hurricane impacts, but lingering effects may be more costly.  The general public derided many of the forecasts as inaccurate or unreliable, saw sensational coverage from outside media sources, and were subject to considerable disruptions associated with school, road, and government closures despite no actual flooding in town. These circumstances may contribute to a decreased likelihood to act on emergency decrees in the near future.

In the coming months, CLIMAS researchers will work with regional planners and officials to further explore the experience of Odile as it relates to emergency management planning and forecasting.

Monsoon Recap - June 15 - Sept 30, 2014

Friday, October 17, 2014

Looking back on the 2014 monsoon, a simple characterization of the season as ‘normal’ or ‘average’ (or above or below these thresholds) is difficult, given the spatial and temporal variability of monsoon storms. The cumulative seasonal totals provide one way of characterizing the monsoon, and by those metrics, the Southwest saw an average to above-average summer rainy season, with much of Arizona and New Mexico receiving well above-average rainfall. 

Most of Arizona received well above-average monsoon rainfall—200 to 400 percent of average—and many     areas in the state registered 150 percent of their seasonal total or higher. The exceptions were across most of the Four Corners region and in portions of Pima, Pinal, and Graham counties (Fig. 1a). Precipitation intensity (Fig. 2a) identifies areas that received a significant portion of their monsoon precipitation in a few extreme events, with the Phoenix metropolitan area and portions of western Arizona being prime examples of more intense precipitation. Figure 3a (the percentage of days observing 0.01 inch of rain or more) further illustrates this pattern by highlighting areas that received more frequent and steady rain (e.g., much of the southeastern portion of the state) compared to areas with much less frequent rain (e.g., Phoenix, western Arizona, and the Four Corners region).

New Mexico saw a similarly strong, if not stronger, monsoon, with most areas of the state receiving more than 200 percent of their seasonal average and large swaths of southern New Mexico recording between 300 and 400 percent of their seasonal average (Fig. 1b). The exceptions were the Four Corners region and the northeastern corner of the state. New Mexico monsoon precipitation intensity (Fig. 2b) shows a relatively even pattern, with more widespread coverage and less variability compared to Arizona. The graphic depicting percent of days with rain in New Mexico (Fig. 3b) shows larger areas of more frequent but less intense precipitation, with a large percentage of the state experiencing measurable precipitation on at least a third of days during the monsoon.

The variability and intensity of these storms is only hinted at in seasonal totals however, and the monsoon is notoriously spatially variable and inconsistent. It is not uncommon for 1–2 inches of rain to fall in midtown Tucson and be dry in the foothills, or vice versa, for example, and many metrics are based on the placement of a limited number of rain gauges. This is an important point because during numerous precipitation events this season, a single storm dropped a season’s worth of rain in a day (and in a few cases, in a few hours), but the coverage was not always consistent or uniform. 

These storms also drive above-average seasonal totals, which has a limited effect on mitigating drought compared to steady and consistent rains, increase disaster potential due to intense precipitation (e.g., Tropical Storm Norbert in Phoenix and Tucson), and underscore the complexity of planning a large urban area for a possible storm event (e.g., Tropical Storm Odile in Tucson). Citizen science enterprises such as rainlog.org provide a more detailed and nuanced picture of monsoon variability through crowdsourcing of precipitation measurement, but the standard measure is still a comparison of the seasonal totals measured at stations in the Southwest (Fig. 4). The intensity and percent of days with rain (Figs. 2-3, above), help illustrate different patterns of steady vs. intense precipitation, but cumulative monsoon precipitation plots also help clarify variation in precipitation intensity.

Three plots (Figs. 5-7) help explain these different types and intensities of rain events. In September, Phoenix (Fig. 5) received almost all of its monsoon precipitation in two single days, and a majority of the rain fell in a single day when Norbert pushed in from the Gulf of California on Sept. 7. The precipitation plot for the Coronado National Monument (Fig. 6) shows a much more even precipitation pattern, with numerous smaller storms spread out over the season; the largest single-day rain event was associated with the incursion of moisture from Odile). The precipitation plot for Tucson (Fig. 7) falls in the middle, with more frequent and smaller storms compared to Phoenix, but longer dry spells and gaps in monsoon precipitation compared to Coronado NM HQ. Norbert is also clearly identifiable in this plot.

This comparison helps illustrate that while extreme precipitation events may provide short-term drought relief and precipitation totals may indicate water deficit improvements, long-term drought conditions will persist and are best mitigated by similarly long-term patterns of above-average precipitation, especially as we look forward to the winter precipitation season.

This post was originally published as part of the October 2014 Southwest Climate Outlook

2014/2015 El Niño Tracker: Oct 16, 2014

Thursday, October 16, 2014

An El Niño Watch, issued by the NOAA Climate Prediction Center (CPC), continues for the seventh consecutive month as signs of an emerging El Niño are just on the horizon, but not quite here yet. Another slug of warm water (also known as a Kelvin wave), has been making its way across the Pacific Ocean from west to east just below the surface and is poised to emerge and help warm sea surface temperatures in the eastern Pacific over the next month or so. Westerly wind bursts, which help move this warmer-than-average water to the east, have occurred in the western and central Pacific but have been temporary and haven’t helped sustain a steady progression towards El Niño conditions, which typically peak during mid-winter. 

Forecast models are betting the current Kelvin wave and associated warm water in the east Pacific will finally get this fickle event to organize and roll forward as a weak El Niño; only a handful of models suggest a moderate-strength event. The early-October consensus forecast (Fig. 1) issued by the International Research Institute for Climate and Society (IRI) and the CPC still indicates more than a 65 percent chance of El Niño conditions developing during the November-December-January period and most likely persisting through early next spring. The impacts associated with weak El Niño events are much less certain than with stronger events, with similar past events bringing both dry and wet conditions to the Southwest U.S. during the winter. Seasonal precipitation forecasts still indicate an enhanced chance of above-average precipitation over the upcoming winter, but confidence in this forecast has wavered slightly because of the expected weak nature of the emerging El Niño. 

This post was originally published as part of the October 2014 Southwest Climate Outlook

Monsoon Summary (June 15 – Sep 18)

Friday, September 19, 2014

We are nearing the end of the 2014 season, and while it is difficult to characterize the highly variable day-to-day storms of any monsoon as “normal,” we have had a fairly typical if not above-average monsoon season in terms of precipitation. Regional assessment is complicated by the effects of a few extreme events that amplified precipitation amounts in parts of Arizona and New Mexico and caused an entire month’s or year’s worth of precipitation to fall in a single storm.

Southeast, southern, west-central, and the high-elevation areas of central Arizona have all seen impressive monsoon totals, with precipitation ranging from 200 to 400 percent of average. Most of Arizona, in fact, has seen above-average seasonal monsoon precipitation (100-200 percent of average) with the exception of the Four Corners region, which is struggling with below-average precipitation and long-term drought (Figure 1). The intensity of these storms, measured as the ratio of total precipitation over the time period to the number of days observing rain, in inches per day (Figure 2), reveals that some areas—western Arizona in particular—received a significant portion of their monsoon precipitation in a few extreme events, and in some cases a single storm. These intense storms offer little in the way of long-term drought relief but pose major threats in terms of their destructive potential, especially in urban/metropolitan areas. Figure 3 (the percentage of days observing 0.01 inch or more) illustrates which areas received more consistent and steady rain.

New Mexico has seen a strong monsoon as well, with most of the state receiving well-above-average precipitation, and large portions of central and southern New Mexico receiving 200 percent or greater of average precipitation. As with Arizona, the Four Corners region is below average, as is the northeastern corner of the state (Figure 4). Maps of the intensity and frequency of monsoon precipitation in New Mexico (Figures 5 and 6, respectively) show larger areas of more frequent, less intense storms. This precipitation should help mitigate short-term drought conditions, but long-term deficits remain.

Tropical storms have been active in the Pacific, and while early-season storms veered into the Pacific Ocean, recent storms (Marie, Norbert, and Odile) have followed the later-season pattern of re-curve into the Pacific coast, boosting precipitation in the Southwest (albeit in a highly variable way). Norbert caused considerable flooding in Phoenix and to a lesser extent in Tucson, and on September 17 Odile caused most of southern Arizona and New Mexico to brace for the worst, with projections of 3-6 inches of rain for those in the direct path. The storm eventually swung south, and most of the impacts were felt in northern Mexico and far-southern Arizona (Figure 7).

This post was originally published as part of the September 2014 Southwest Climate Outlook

El Niño Tracker - Sept 2014

Thursday, September 18, 2014

The song remains the same this month with El Niño not quite here yet, but probably soon. This is now the seventh consecutive month since the NOAA Climate Prediction Center issued an “El Niño Watch” last March. The signs are a bit stronger once again, but it is getting late in the game since El Niño events take several months to build up and typically peak during the mid-winter months. Another slug of warm water (known as a “Kelvin Wave”) has been making its way across the Pacific Ocean from west to east just below the surface and is poised to emerge and help warm sea-surface temperatures in the eastern Pacific over the next month or so. There has also been some activity in the western and central Pacific called “westerly wind bursts” which can help move this warmer-than-average water to the east, but the bursts have been temporary and haven’t helped sustain a steady progression towards El Niño conditions. 

Forecasts models are predicting the current Kelvin Wave and associated warm water in the east Pacific will finally get this fickle event to organize and roll forward as at least a weak El Niño. The mid-September consensus forecast (Figure 1) issued by the International Research Institute for Climate and Society (IRI) and the NOAA Climate Prediction Center (NOAA-CPC) still indicate a greater than 70 percent chance of El Niño conditions developing during the November-December-January period and most likely persisting through early next spring. Most models indicate that the event will ultimately peak at a weak strength, with only a handful of models suggesting a moderate-strength event. The impacts associated with weak El Niño events are much less certain; past events have brought both dry and wet conditions to the southwest U.S. during the winter season. Seasonal precipitation forecasts still indicate an enhanced chance of above-average precipitation over the upcoming winter season, but confidence in this forecast has wavered slightly because of the expected weak nature of the emerging El Niño event.

This post was originally published as part of the September 2014 Southwest Climate Outlook

Monsoon Summary (June 15 - Aug 19)

Friday, August 22, 2014

The 2014 monsoon can be characterized many ways—the amount and intensity of rain has been spotty both spatially and temporally, the humidity has been persistently high, and precipitation has improved short-term drought conditions in many areas. Certainly it cannot be characterized as a dud. 

With about a month remaining in the 2014 monsoon season, southeast Arizona, the higher elevation areas in central Arizona, and west-central Arizona have generally experienced above-average precipitation (Figure 1). West-central Arizona historically experiences less monsoon rainfall and more infrequent storms then other regions, and this year only a few storms have generated most of the observed rainfall in this region. Consequently, west-central Arizona boasts higher storm intensity, a metric that takes the total accumulated precipitation and divides it by the number of days with precipitation. Using this metric, west-central Arizona has an intensity of 0.5 inches per day; many of the higher elevation regions also have a similar intensity, where as the desert values are less than 0.2 inches per day. A notable exception occurs around Phoenix where 2–3 inches of rainfall fell on August 19 (with some nearby stations tallying as much as 5–6 inches) and caused severe flash flooding. In New Mexico, precipitation has been above average across most of the state and in particular within the Rio Grande basin (Figure 2). Consequently, short-term drought conditions have improved in recent weeks, although water storage is still low from the accumulated impacts of below-average winter rain and snow over the last decade. 

The frequency of rain tells another story and shifts the focus to southeastern Arizona. In this region, precipitation greater than 0.1 inches has fallen during half of the days since June 15 (Figure 3). Most rain gauges in this region have measured near-average or above-average precipitation. Monsoon storms have also been frequent in New Mexico, with most of the state experiencing rainfall on half of the days since June 15 (Figure 4). 

Tropical storm activity in the eastern Pacific Ocean has also been active, although all eight of the named cyclones have tracked westward away from the North American continent. Hurricane activity is expected to continue through October; this could bring even more moisture to the Southwest, as some of the biggest floods on record have occurred from decaying tropical storms wafting over the region.  

This post was originally published as part of the August 2014 Southwest Climate Outlook

El Niño Watch - Aug 21, 2014

Thursday, August 21, 2014

An “El Niño Watch” continues this month as issued by the NOAA Climate Prediction Center several months ago. The watch is just that: we are waiting and watching for the development of a full-fledged El Niño event that has yet to materialize across the equatorial Pacific Ocean. Several indicators of El Nino-Southern Oscillation (ENSO) status declined, moving back towards ENSO-neutral values over the past month instead of leaning towards an El Niño event as they had been.  These shifts included slight cooling in the eastern Pacific Ocean and near-average wind patterns along the equator (Figure 1). But for those cheering on the development of an El Niño event, not all hope is lost. A slug of warm water just below the surface has materialized in the western Pacific Ocean and is slowly moving eastward.  This is similar to the pulse of warm water that led to dramatic warming in the eastern Pacific Ocean earlier this spring. This “Kelvin Wave” is not as strong in magnitude as the earlier springtime wave, but is expected to surface in the eastern Pacific over the next several months, pouring fuel back into the El Niño engine.

Seasonal ENSO outlooks pick up on this pattern and remain rather bullish in suggesting that an El Niño event is likely later this fall that would peak in early winter (Figure 2). The models suggest this would be a moderate event at best; in fact most models suggest a weak El Niño event of around 1 degree C above average in sea-surface temperatures in the central/eastern Pacific Ocean. The weaker the event, the trickier the forecast with respect to expected precipitation across Arizona and New Mexico. Weak El Niño events vary between wet, near average, and even dry winters in historical records across the Southwest. Official seasonal precipitation forecasts continue to suggest an enhanced chance of above-average precipitation across Arizona and New Mexico through the winter, but confidence in these forecasts is tied to the development and ultimate strength of the El Niño event that has yet to materialize.

This post was originally published as part of the August 2014 Southwest Climate Outlook

Recap: Drought and Water Supplies in the Southwest - 1075' Shortage on the Colorado River

Wednesday, August 13, 2014

This week, we released the 5th episode in the CLIMAS podcast series[1] 1075' - Shortage on the Colorado River, which explores what a shortage declaration on the Colorado River would mean to those living in the Southwest. 1075 refers to the elevation of Lake Mead – in feet above sea level – that serves as the trigger for shared shortage restrictions[2].   Any shortage declaration before 2026 would be the first under the 2007 Interim Guidelines[3].  After years of drought and ever-increasing demands on the river, the latest projections from the Bureau of Reclamation suggest the lake could drop below 1075 sometime in  2015.  

Water availability and potential shortages are a persistent concern for the Southwest, and careful management and creative conservation efforts are a requisite part of a sustainable water use plan for the region.  We knew this was a timely and relevant issue when we planned and recorded the series over spring and summer 2014, but we didn't anticipate the media frenzy that led to more sensationalistic media coverage of Lake Mead levels specifically, and water issues in the west more generally.

The media attention reinforced our goal of "attempting to demystify the rules and regulations that govern water use on the Colorado River and discuss what it means to the people and sectors across Arizona when a shortage occurs..." and of "exploring the opportunities and consequences of a shortage to construct a nuanced view of a complex issue."  The negative side is often what receives the most attention. But, perhaps a shortage will spur innovation and lead to better conservation that saves money. At the most fundamental level, we wanted to know if Lake Mead falling below 1075 would be looked back upon as a moment in history that 'changed everything' or if this seemingly inevitable moment would feel a lot like the Y2K craze.

We turned to regional water experts to help us better understand Southwest water supply issues, the Central Arizona Project, realities of water management, opportunities for conservation, and details on what will actually happen if - and more likely when - a shortage declaration is made in the next few years.

Episodes

  • In Episode 1: Management of the Colorado River, Zack Guido and Ryan Thomas interview Doug Kenney about the management and history of the Colorado River, who uses the water, and what a potential shortage could mean for the system.  This is an excellent and detailed overview of Colorado River management issues, and is an excellent foundation for subsequent episodes.
  • In Episode 2: Stressors on the River, Zack sits down with Bonnie Colby, Geroge Frisvold, and Kiyomi Morino to discuss specific stressors on the Colorado River Basin, how these stressors may change over time, and how these changes may affect management and behaviors across the Southwest.
  • In Episode 3: Shortage Impacts on the Central Arizona Project, Zack and Ryan are joined by Mohammed Mahmoud of the Central Arizona Project (CAP) to the role that CAP plays in delivering Colorado River water throughout Arizona, as well as implications for the CAP system if/when a shortage declaration is made.
  • In Episode 4: The Central Arizona Groundwater Replenishment District Zack interviews Dennis Rule of the Central Arizona Groundwater Replenishment District (CAGRD), to get into details about the CAGRD in the management of Arizona groundwater, and potential impacts on the system from continued drought in the Colorado River Basin.
  • In Episode 5: Tucson Water and Municipal Water Issues Zack sits down with Alan Forrest, the Director of Tucson Water, and they discuss strategies that Tucson implemented to deal with potential water shortages, the conservation and recapture efforts of municipalities in Southern Arizona, and the practical realities of providing municipal water to an growing population in the southwest.

Background

These issues (Lake Mead levels, water management concerns, etc.) didn't pop up out of nowhere.  The social, environmental, and management context are the backstory - and the experts we interviewed helped us capture some of the nuance, but it's also important to highlight a few threads that contributed to the ongoing conversation.

Stories and reports about drought conditions, especially in California and Texas, brought contemporary water issues to the forefront over the past year or so [4].  Attention ramped up this spring and summer as media outlets picked up in on a new study highlighting higher than predicted groundwater consumption estimates, especially in the southwest (see this map).  Media coverage focused on this story, as well as the drop in water levels at Lake Mead, often conflating groundwater and surface/allocation water issues.  Coverage veered into the sensational, as stark images of dry conditions dominated the coverage, while the headlines were filled with portents of doom.  The added attention can help bring energy and ideas to critical issues in need of timely solutions, but it can also confuse audiences when they see headlines predicting societal and environmental collapse.  These problems persist long after media attention has waned, and managers must respond to the aftermath of this style of coverage, focusing on practical solutions and maintaining good working relationships with a diverse network of stakeholders (some of whom are alienated from the process by overly binary or simplistic pronouncements of any political flavor).

As is often the case, this wasn't even the first time this had been written about in detail, and a number of journalists and scientists have been giving this issue careful consideration as it unfolds.  John Fleck has been tracking this issue in detail, and has a number of insightful posts (Lower CO Basin New Years Resolution - 2012 - The Colorado River Doomsday Clock - 2013), including a one earlier this summer detailing CAP strategies for management, and his most recent entry addressing specific challenges (and possible implications) of the results outlined in the Castle et al. study.  Fleck also wrote about policy implications for this study, detailing flexibility in the Colorado River System thus far, as well as how groundwater usage complicates management plans and outcomes.  Brian Devine wrote about the consequences of agricultural to municipal water transfers, as well as more general questions about conservation, and Doug Kenney and Kimery Wiltshire used the record low level in Lake Mead to frame a discussion of implications for shortages and strategies for management and conservation.

The point? - a number of people have been thinking about this for a long time - and we hope that by turning to a few of these experts, both in the framing of why we did this podcast, and who we were able to bring in for conversations, we can present a nuanced take on the very real challenge of water management in the Southwest, but without losing sight of the strategies that have worked and are working to protect this limited resource.  Stay tuned - we plan to expand this conversation to include additional perspectives on this issue.

Notes

  1. We may do a second "season" given all the interest in the series, especially since there are numerous other experts we would love to talk to, and other sectors (e.g. ranching, agricultural, industrial) that we would like to include in the conversation.
  2. Note: Mead elevation falling below 1075' in a given month does not automatically trigger shortage restrictions. The January 1st forecast from the August 24-month study is the Mead elevation value that determines if a Tier 1 Lower Basin shortage will occur. The 24-month study is a monthly report produced by the Bureau of Reclamation to keep track of Colorado River system reservoirs. So even if Lake Mead is forecasted to drop below 1075' in mid-2015, shortage is not declared unless the 2014 August 24-month study forecasts a January 1st Mead elevation at or below 1075'.
  3. There was a shortage declared in 1963/1964 when Lake Powell was filling. Drought caused low inflows into Lake Mead and deliveries to the Lower Basin were subsequently cut.  
  4. There was some hope that a stronger El Niño might alleviate some of the drought conditions, but as predictions for a strong El Niño event have waned, so has that optimism.

Many thanks to Dr. Mohammed Mahmoud (of the Colorado River Programs / Central Arizona Project) for providing the clarifications in footnotes [2-3].

Monsoon Summary (June 15 - July 15)

Friday, July 18, 2014

Originally published in the Southwest Climate Outlook, released the 3rd Thursday of every month.  Sign up for email newsletter version.


Monsoon storms began around July 3 in many parts of southern Arizona. The average onset date of the monsoon in southeast Arizona is between July 1 and 6 (Figure 1). In months that preceded the monsoon, climatologists speculated that a developing El Niño event could delay the onset, an interpretation based on past analogs. This did not occur, in part because the atmosphere has yet to respond to the El Niño, despite warmer-than-average sea surface temperatures (SSTs) in the tropical Pacific Ocean (see El Niño Watch for details). 

Many parts of Arizona received above-average precipitation last month thanks to monsoon rainfall (Figure 2). The spotty nature of the monsoon, however, belies sweeping characterizations that apply to all regions because above- and below-average rainfall is often experienced over short distances not captured by more sparsely located rain gauges. The Prescott area of Arizona, for example, has not yet been doused as much as other areas. Nonetheless, many weather stations in southeastern Arizona have measured above-average rainfall since June 15. These include the Tucson International Airport and airports in Douglas and Nogales, where rain has measured 1.61, 2.59, and 3.4 inches since June 15, respectively. These totals amount to 0.45, 1.01, and 1.14 inches above average, respectively. Sierra Vista logged 4.87 inches of rain—3.36 inches above average. 

Many places around Arizona have felt above-average humidity. This is reflected in dewpoint temperatures, which increase as moisture content in the air increases, across the state. In Tucson, for example, dewpoints often have been above 60 degrees F (Figure 3), as they have in Phoenix and Yuma. These humidity levels indicate that moisture is present and, if other conditions converge, storms will result. The intensity and geographic coverage of the storms, however, also depend in part on atmospheric temperature gradients that enable air to rise, condense, and squeeze out rain, and on the presence of winds aloft that push storms off the mountains. Even if rain does not fall, higher levels of humidity help suppress fire risk, and fire restrictions across the regions are being eased.

While southern Arizona generally has experienced an active monsoon thus far, the opposite story has evolved in southern New Mexico and southwest Texas (Figure 2). El Paso, for example, has only received 0.32 inches of rain, or about 0.8 inches below average. The position of the high pressure system, which has largely been centered north of southeast Arizona, has helped create this juxtaposition. On the western, Arizona side of the system, moisture-laden air has been streaming from the south, whereas dry air has been wafting from the north on the eastern, New Mexican side.

El Niño Watch - July 18, 2014

Friday, July 18, 2014

Originally published in the Southwest Climate Outlook, released the 3rd Thursday of every month.  Sign up for email newsletter version.


The El Niño event that has been anticipated for the past several months continues to suffer from stage fright; it has yet to fully materialize across the equatorial Pacific Ocean. Nonetheless, forecasts remain bullish that an El Niño will form in coming months, and consequently the El Niño Watch is still in place. Probabilities that an El Niño will fully materialize this fall and winter reach slightly more than 70 percent, according to the mid-July ENSO forecast issued by the NOAA-Climate Prediction Center (CPC) and the International Research Institute for Climate and Society (IRI; Figure 1). These high probabilities reflect above-average sea surface temperatures (SSTS) in the far eastern Pacific and weak westerly winds in the central Pacific. Belief that this event will evolve into a strong El Niño, however, has lost muster because SSTs have hovered slightly above average and not steadily climbed (Figure 2). In addition, the atmosphere has failed to cooperate in a manner consistent with above-average SSTs. For an El Niño to gain strength, the warming SSTs in the central Pacific need to be accompanied by a subsequent weakening of the easterly trade winds which, in turn, reinforce warm SSTs. The easterly winds have yet to slacken as much as expected.

Nonetheless, the CPC forecast suggests that both the ocean and atmosphere are transitioning to and ultimately will become an El Niño. Feeding this expectation is the observation that convection in the central Pacific has become more organized in recent weeks. This indicates a growing atmospheric connection with the SSTs that could eventually lead to a weakening of the trade winds. Moreover, many of the dynamical forecast models (those that included both ocean and atmosphere dynamics) suggest a rapid warming in the central Pacific during the August–October period, with the El Niño event peaking in mid-winter of 2014 and 2015. Although the ultimate strength and duration remains uncertain, a weak to moderate event appears the most likely outcome, and the CPC notes the possibility for a strong event has diminished greatly in the past several months.

El Niño events tend to bring wetter conditions to the Southwest during the winter (Figure 3), with moderate and strong events delivering higher chances for above-average precipitation. However, if the El Niño event is weak, the precipitation outlook for the upcoming fall and winter becomes more uncertain. The strength and duration of the event should become clearer over the next two months as ocean and atmosphere signals lock in to each other.

Arizona Facing High Fire Danger a Year After Yarnell

Tuesday, July 1, 2014

Originally published, June 30, 2014 on the UA News Blog


It was one year ago that lightning struck and ignited the Yarnell Hill Fire, a devastating wildfire that resulted in the deaths of 19 firefighters who were members of the Granite Mountain Hotshots. This year, a combination of drought conditions, high winds and high temperatures all call for an intense fire season. Predictions indicate above-normal fire potential, and indicators suggest the onset of the monsoon season will be delayed.

Photo: High Park Fire - Creative Commons

Since October, we've had very low precipitation – averaging less than half of average across large portions of the state – accompanied by low snowpack and temperatures that have been well above average.

The combination of these factors, along with bursts of dry winds that are typical for the spring, gives us conditions of above-normal fire potential, which is what the Southwest Coordination Center, the main fire prediction center for our region, predicted beginning in late January.

And the setup for this year's fire season is ongoing drought, which affects every part of the state. The U.S. Drought Monitor characterizes drought in Arizona as severe across most of the state, and as extreme in Yavapai County and much of the southeastern quarter of the state.

As of June 24, Arizona wildland fire totals, not including prescribed fires, were 139,378 acres from 783 human-caused and 50 lightning-caused fires. The total acres burned thus far exceed the median acres burned for the state for the whole fire season.

In southern Arizona, we are just past the median date of peak seasonal fire danger, but the date can vary by two weeks in any given year. Peak seasonal fire danger for northwestern Arizona, including Yavapai County where the Yarnell Hill Fire occurred in 2013, is right now – June 30 through July 1 – according to maps provided by the Southwest Coordination Center. And, earlier this year, the Southwest Coordination Center predicted above normal fire potential for mid-May through mid-July, for the southeast quarter of Arizona, stretching northwest into Yavapai County.

The current "energy release component," which indicates how hot a fire could burn, is very high and is above 2013 levels across much of Arizona. This is just one measure of fire danger commonly used by fire analysts, expressing the potential intensity of a fire given the moisture content of fuels.

While it is not surprising at this time of year to see high short-term fire danger and above normal long-term potential for Arizona fires to require extra outside resources, such as air tankers and teams with highly specialized skills for fighting fires for putting out fires – this year's levels of fire danger are exceedingly high.

Any fire is devastating to the local community, and Arizona fires can have a lingering effect on the landscape, with post-fire effects such as flooding and debris flows. It is notable that we have not suffered an enormous Wallow or Rodeo-Chediski sized fire. The Slide Fire, which burned in Oak Creek Canyon in May and early June, was severe and it occurred in very steep terrain, which increases the chances of post-fire impacts. It is a testament to the fire-fighting community and its heightened preparedness for this year's fire season that the Slide Fire did not consume even greater acreage than the 21,227 acres burned by the fire.

Looking ahead, the arrival of summer monsoon precipitation is the key to putting a lid on Arizona's high fire potential.

However, the monsoon is notoriously difficult to predict. And predicting the arrival of the monsoon is even more difficult. Nevertheless, the Southwest Coordination Center predicts a delay to the start of the monsoon. Based on comparisons with previous years that had conditions similar to 2014, the Coordination Center predicts more reliable monsoon rains east of the Continental Divide, in New Mexico. Center specialists also note that less reliable moisture on the Arizona side of the divide can lead to the possibility of continued significant fire activity into July and possibly August.

See tips on how to prevent wildfires in this post.


Gregg Garfin is Deputy Director for Science Translation & Outreach, Institute of the Environment, University of Arizona