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Southwest Climate Podcast: Monsoon Frequency vs. Intensity, & El Niño Still Dragging its Heels

Tuesday, August 26, 2014

In the August Southwest Climate Podcast, Zack Guido and Mike Crimmins talk about variability and timing of monsoon precipitation, and why frequent and sustained moisture might matter more than heavy infrequent rains (for drought, especially).  El Niño is still dragging its heels, but it still looks good for a weak to moderate event this winter.  Interspersed throughout, Zack and Mike answer questions submitted by listeners, including "weather" vs. "climate" and how the monsoon is a good way to think about this distinction, and whether the monsoon and El Niño can really help with a long term drought.  

If you have a question you'd like answered, you can email Zack Guido (zguido@email.arizona.edu) or Ben McMahan (bmcmahan@email.arizona.edu) with "CLIMAS Podcast Question" in the subject line.  You can also tweet us @CLIMAS_UA or post a question on facebook

 

Notes from an Applied Climatologist: Tropical Storms and the Southwest Q&A

Tuesday, August 26, 2014

 

How do (Pacific) tropical storms affect the weather patterns of the SW?  What type of tropical storm paths affect weather in the SW? 

Figure 1: Tropical Storm Formation by Date - Source: NOAAFigure 2: Pacific Moisture Flow into Southwest - Source: NOAAThe eastern Pacific Ocean along the west coast of Mexico and central America are an active area of tropical storm formation through the summer and early fall (typically between June and September) (Figure 1). Warm water and light winds create the perfect conditions in this region for thunderstorms to flare up, and eventually organize into tropical storms and hurricanes.

Surprisingly, the landlocked southwest U.S. is impacted by these storms in a variety of ways. The most common way is by inducing surges of moisture up the Gulf of California into Arizona that can fuel widespread outbreaks of monsoon season thunderstorms.

Clusters of storms or tropical systems that pass near the mouth of the Gulf of California can produce a cool outflow of winds and create a pressure differential up the Gulf of California (high pressure near the cool thunderstorm outflows and low pressure near the hot conditions and rising air typical in the lower Colorado River valley at the north end of the Gulf). This pressure differential leads to the surge of moisture traveling from south to north, up into the low deserts of Arizona, and sometimes southern California (Figure 2).

Tropical storms and hurricanes in the eastern Pacific can sometimes actually impact the Southwest through a direct hit (Figure 3). Easterly winds will typically carry eastern Pacific storms west out to sea, but storms that take a more northwesterly track along the Mexican coast can eventually track north or even northeast. This typically happens later in summer or in early fall, as the subtropical high pressure system retreats south giving way to very light winds aloft in no particular direction or stronger westerly winds advancing from the north, the sign of fall and winter approaching. When tropical storms move north and aren’t steered away from the coast of Mexico they can continue to wander north or can get caught up in westerly flow aloft and directed inland towards southern California and Arizona.

Figure 3: Historical Tropical Storm Tracks in the SW, Figure 4: Hurricane Octave Flooding 1983 - Source: NOAA

Hurricanes weaken quickly when they encounter land and break away from their energy source of warm ocean water, so only weak tropical storms or ‘remnant low’ pressure systems actually make it to inland locations like Arizona. Still, these systems are often potent rain producers bringing with them abundant moisture and a source of lift to produce widespread thunderstorms and can produce very dangerous and widespread flash flooding events. The infamous flash flooding disaster that occurred in October of 1983 was caused by tropical storm Octave where much of Arizona observed record precipitation and catastrophic flooding (Figure 4).

Michael Crimmins is an Associate Professor and Climate Science Extension Specialist in the Department of Soil, Water and Environmental Science

Figure 1: Tropical Storm Formation by Date - Source: NOAA
Figure 2: Pacific Moisture Flow into Southwest - Source: NOAA
Figure 3: Figure 3: Historical Tropical Storm Tracks in the SW - Source NOAA
Figure 4: 1983 - Hurricane Octave and Flooding in the SW - Source NOAA

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

Notes from an Applied Climatologist: Q & A on El Niño, Predictions, and Indices

Wednesday, August 13, 2014

 

What is the criteria to call something El Niño?  Is El Niño a continuum or is there a binary switch where it's either an El Niño event or not?

There are actually several different indices or metrics used to track the state of ENSO (the El Niño-Southern Oscillation) across the Pacific Ocean and whether oceanic and atmospheric patterns reflect El Niño, La Niña or neutral conditions. Some of these indices look just at the atmosphere (for example Southern Oscillation Index), some just at the ocean (for example Niño3.4 index) and some the combination of both (for example the Multivariate ENSO Index). All have different strengths and weaknesses, but oceanic based indices tend to reflect the more slowly evolving part of ENSO, the shift in sea surface temperature patterns, which in turn can have an impact on global weather patterns over many months or seasons.

The NOAA Climate Prediction Center uses the Oceanic Nino Index (ONI) which is the running 3-month average of sea surface temperature anomalies (or departures from average) across a key part of the central equatorial Pacific from just west of the International Date Line back towards the east to 120W longitude.

Tracking sea temperatures in this region provides a good indication of whether or not tropical convection (which is driven by warm waters) is shifting or may soon shift unusually far east along the equator during El Nino conditions or far west during La Nina events. ONI values typically range from -2.5 which would be indicative of a strong La Nina to 2.5 which would be a strong El Nino event. The NOAA-CPC makes a distinction between the emergence of El Nino or La Nina conditions which would be ONI values climbing past the +0.5 (El Nino) or -0.5 threshold at the monthly scale as well as other atmospheric indications like shifts in wind and rainfall patterns versus a full blown event that lasts for many months or over seasons. An event requires ONI values to be greater than the +0.5 or -0.5 threshold for at least five consecutive months (more details at climate.gov)

 

How closely linked is the strength of El Niño with observable effects in the Southwest?  Would a weak El Niño look that different from no El Niño at all?  

The strength of an El Nino event does seem to matter with respect to seasonal climate connections here in the Southwest. Looking at past precipitation patterns during El Nino winters of varying strengths, you notice that strong events (ones with ONI values >1.5) tend to have a more reliably wet look to them versus weak events which vary from above-average to even below-average.

The forecast of a strong El Nino event tends to lead to a subsequently more confident outlook in wet conditions for Arizona and New Mexico. If the event is forecasted to be weak or even moderate the outlook for precipitation over the upcoming winter season is much less certain (more on this topic climate.gov)

Michael Crimmins is an Associate Professor and Climate Science Extension Specialist in the Department of Soil, Water and Environmental Science

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].

1075' - Shortage on the Colorado River Ep. 5 - Tucson Water & Muncipal Water Issues

Tuesday, August 12, 2014

Lake Mead from the Hoover Dam - Source: Wikipedia Commons

1075’ – Shortage on the Colorado River is a CLIMAS podcast series that explores what the first ever 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[1]. While this has never happened before[2], 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[3] as soon as early 2015.

In this series, we attempt 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. This series will explore the opportunities and consequences of a shortage to construct a nuanced view of a complex issue.

  • Episode 5: Tucson Water and Municipal Water Issues (Alan Forrest) - In this episode, CLIMAS climate scientist Zack Guido speaks with Alan Forrest, Director of Tucson Water, about various strategies that Tucson implemented to deal with potential water shortages, the conservation and recapture efforts that areas of municipalities in Southern Arizona, and the practical realities of providing municipal water to an growing population in the southwest.

 


Alan Forrest is Director of Tucson Water, a municipally owned water utility serving a population of over 700,000 (250,000+ services) in the Tucson and Pima County Area in SE Arizona.  He is one of Arizona's recognized experts in water management, and began his municipal water career at Tucson Water in the 1980's.  He has worked on water and municipal water issues in Southern Arizona for over 30 years, in both the public and private sectors.


[1] 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'.

[2] Any shortage before 2026 would be the first declared shortage under the 2007 Interim Guidelines. However, there was a shortage declared in 1963/1964 when Lake Powell was filling up. Drought caused low inflows into Lake Mead and deliveries to the Lower Basin were subsequently cut.

[3] The Applied Climate Science Group in the School of Natural Resources at the University of Nebraska-Lincoln has compiled an impressive array of photos and data relating to the drop in Lake Mead levels - be sure to check it out!

Many thanks to Dr. Mohammed Mahmoud (of the Colorado River Programs / Central Arizona Project) for providing the clarifications in footnotes [1] and [2].

Notes from an Applied Climatologist: El Niño & Drought Q&A

Wednesday, August 6, 2014

 

There’s been a lot of talk about El Niño and ‘busting the drought'.  How much can El Niño help with ongoing drought conditions in the West?

The El Niño event struggling to form in the Pacific Ocean has been a ray of hope for many of us across the Southwest for several months now looking for some relief from both short and long-term drought conditions that have plagued California, Arizona and New Mexico for several years now. The important thing to remember is that we can only expect *some* relief in a best case scenario with a strong El Niño event delivering abundant precipitation across the Southwest over the winter season. Current drought conditions have accumulated over years and cannot be erased by a single wet season. We can look back at drought indices around the time of the last strong El Niño event over the winter of 1997-1998.

For a detailed look at Standardized Precipitation Index (SPI) in Arizona - Click Here

Wet conditions were observed across Arizona over several months which dramatically improved short-term drought conditions (months to seasons), but longer term drought conditions (seasons to years) were still present and quickly intensified as dry conditions returned the following year. At this point we will need several years of average to above-average precipitation over each season to alleviate long-term drought conditions. An El Niño winter with above-average precipitation would help, but is not a silver bullet at this point.

 

Significant amounts of rain fall during the monsoon, why doesn’t that solve our drought problems?

Monsoon precipitation is a critical water source to many ecosystems and agricultural activities (e.g. ranching), and is an important determinant of drought status during the summer across the Southwest. If monsoon precipitation is spotty, late in onset, and overall below-average, short-term drought conditions can quickly intensify across Arizona and New Mexico. As far as long-term drought conditions that evolve over multiple seasons or years, a single monsoon season typically has little impact.

Dry conditions during the summer can contribute to long-term drought impacts like stress in trees and reductions in surface water streamflows, but average to wet conditions often don’t contribute much to improvements. Monsoon precipitation typically falls in torrents of heavy rain associated with isolated storms, leaving a patchwork of runoff and wet soil that quickly evaporates back into the atmosphere. Occasionally, large-scale flooding events during the summer can lead to high flows in streams and contributions to reservoirs and subsequent relief from long-term drought impacts, but these events are rare and unpredictable.  


Michael Crimmins is an Associate Professor and Climate Science Extension Specialist in the Department of Soil, Water and Environmental Science

1075' - Shortage on the Colorado River Ep. 4 - CAGRD (Dennis Rule)

Tuesday, August 5, 2014

Lake Mead from the Hoover Dam - Source: Wikipedia Commons

1075’ – Shortage on the Colorado River is a CLIMAS podcast series that explores what the first ever 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[1]. While this has never happened before[2], 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[3] as soon as early 2015.

In this series, we attempt 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. This series will explore the opportunities and consequences of a shortage to construct a nuanced view of a complex issue.

  • Episode 4: The Central Arizona Groundwater Replenishment District (Dennis Rule) - In this episode, CLIMAS climate scientist Zack Guido talks to Dennis Rule, manager of the Central Arizona Groundwater Replenishment District (CAGRD), about the importance of CAGRD in the management of Arizona groundwater and potential impacts on the system from continued drought in the Colorado River Basin.

 


Dennis Rule is the Manager of the Central Arizona Groundwater Replenishment District (CAGRD).  In 1993, the legislature created a groundwater replenishment authority to be operated by the Central Arizona Water Conservation District ("CAWCD") throughout its three-county service area. This replenishment authority of CAWCD is commonly referred to as the Central Arizona Groundwater Replenishment District ("CAGRD"). In 1999, the legislature expanded CAWCD's replenishment authorities and responsibilities by passing the Water Sufficiency and Availability Act. The purpose of the CAGRD is to provide a mechanism for landowners and water providers to demonstrate an assured water supply under the new Assured Water Supply Rules ("AWS Rules") which became effective in 1995. Every ten years, the CAGRD is required by law to submit a Plan of Operation to the Director of ADWR. The Plan describes the activities that CAGRD proposes to undertake in the Phoenix, Pinal and Tucson Active Management Areas ("AMAs") over the next one-hundred years based on continued membership enrollment through 2015.


[1] 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'.

[2] Any shortage before 2026 would be the first declared shortage under the 2007 Interim Guidelines. However, there was a shortage declared in 1963/1964 when Lake Powell was filling up. Drought caused low inflows into Lake Mead and deliveries to the Lower Basin were subsequently cut.

[3] The Applied Climate Science Group in the School of Natural Resources at the University of Nebraska-Lincoln has compiled an impressive array of photos and data relating to the drop in Lake Mead levels - be sure to check it out!

Many thanks to Dr. Mohammed Mahmoud (of the Colorado River Programs / Central Arizona Project) for providing the clarifications in footnotes [1] and [2].

Notes from an Applied Climatologist - July 2014 Rainlog Climate Summary

Tuesday, August 5, 2014

July started off with a bang with moisture and thunderstorm activity moving into Arizona over the 4th of July weekend. This start date for monsoon thunderstorm activity was very close to the climatological start date of July 3rd, as determined by the old dewpoint definition (three consecutive days with average dewpoints >= 54F) in Tucson. The ‘monsoon ridge’ of high pressure was in an ideal position over the first two weeks of July to guide abundant subtropical moisture into the state, providing fuel for almost daily thunderstorm activity across parts of southeastern Arizona and the high country along the Mogollon Rim. 

Rainloggers in southern Arizona near Sierra Vista observed amazing precipitation totals of 5 to 7 inches over the first two weeks of the month. Most other areas observed 1-3 inches during this period with higher elevation areas near Show Low and Flagstaff seeing closer to 2 to 4 inches. Most of the Phoenix metro area saw more dust than rain during this period with thunderstorm outflows pushing large haboobs or dust storms through the area numerous times.

Monsoon Tracker Plots - Find More Here

The monsoon ridge was knocked out of position several times the second half of the month leading to a slowdown in monsoon thunderstorms across much of the state. Parts of southeastern Arizona still managed to pick up several inches of precipitation in a handful of storm events. Several Rainloggers near Douglas observed almost two inches of rain on the 27th with a series of storms that moved along the international border. The Tucson and Phoenix metro areas observed isolated storms during this period with lucky neighborhoods seeing up to an inch of rain, but most observing less than 0.25”.

Overall, July was a pretty typical start to the monsoon with some areas observing very heavy rain and many places with a handful of light events. Most of the state is near average for monthly total precipitation with the notable exception of far northeast Arizona which has observed very little in the way of thunderstorm activity. Temperatures were above average across much of the state with the National Weather Service in Tucson reporting that it was the 13th warmest July on record. Overnight temperatures were the big story this past month with Tucson and Phoenix observing several new high minimum temperatures records or ties. The National Weather Service reports that it was the 3rd warmest for Tucson and 5th warmest for Phoenix on record with respect to July minimum temperatures.

Monsoon Summary Maps


Michael Crimmins is an Associate Professor and Climate Science Extension Specialist in the Department of Soil, Water and Environmental Science