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Monthly Archive

SW Climate Outlook Monsoon Tracker - Sept 2017

Friday, September 22, 2017

The North American monsoon was quiet for much of the Southwest through early July, but mid-July through early August saw an impressive run of storms. July was particularly active in southeast Arizona, where numerous locations approached or set single-month records for precipitation. Since early August, however, Arizona has experienced a widespread shutdown of monsoon activity, while New Mexico has seen more regular precipitation. Seasonal totals (June 15 – Sept 13) for weather stations in regional metropolitan areas range from below to above average (see Fig. 3 from Climate Summary), with the more impressive totals (Tucson, El Paso) resulting from near-record precipitation in July. The second half of August and September so far have been disappointingly below average, or at best near average for many locations. Looking at precipitation maps for specific months, July was mostly above normal (top 33 percent) and much-above normal (top 10 percent) across nearly all of Arizona and much of western and northern New Mexico (Fig. 1). August flipped that script, with most of Arizona and western New Mexico recording below-normal or much-below-normal precipitation, and with a large pocket of dry conditions centered over the Four Corners region even while eastern New Mexico was much-above normal to record wettest (Fig. 2). Looking at the cumulative seasonal precipitation totals moderates the large monthly variations (see percent of normal through Sept. 19; Fig. 3), and reveals a high degree of spatial heterogeneity of precipitation across the region. In other words, it was a normal monsoon.


Another way to assess the dry conditions of the last 30 to 45 days is by looking at the number of days since a rain event greater than 0.05 inches (Figs. 4a-b). These maps highlight widespread areas of Arizona and New Mexico that have recorded 20 or more such “dry days” and much larger areas for which it has been 10-15 days since the last rain event. Variable precipitation is a fundamental characteristic of the monsoon, so these gaps are generally expected to occur. Since the bulk of monsoon precipitation falls during July and August, an extended dry run starting in mid-August will limit the overall seasonal total for the region. We are seeing this now, as seasonal totals are mostly falling close to climatology in spite of the higher expectations that were set over the wet period from mid-July to early August (Fig. 5).

There is still a chance of additional precipitation in the remaining days of the official monsoon (which ends on Sept. 30), but activity during this time of year is often attributable to an influx of moisture from eastern Pacific tropical storms that recurve back into the Southwest, especially later in the tropical storm season. Currently, there are no such events forecasted over the next few weeks, thus the current monsoon precipitation totals are likely to also be the final seasonal totals. September 30 only marks the official end of the monsoon, but not an end to potential moisture influx to the Southwest from tropical storms, as evidenced by numerous October events that have resulted from such activity.

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SW Climate Outlook - ENSO Tracker - Sept 2017

Friday, September 22, 2017

Oceanic and atmospheric indicators remain within the range of neutral but have shifted more towards La Niña conditions in the past month (Figs. 1-2). Seasonal outlooks and forecasts reflect these changes, and most now see La Niña conditions as the more likely outcome for fall 2017, with ENSO-neutral conditions mostly still favored for winter. On Sept. 11, the Japanese Meteorological Agency (JMA) forecast that ENSO-neutral conditions had a 60-percent chance of persisting through winter 2018, but that the chance of La Niña had increased to 40 percent. On Sept. 12, the Australian Bureau of Meteorology ENSO tracker remained at neutral/inactive; they noted that the tropical Pacific is on a cooling trajectory (supporting potential La Niña formation) but that other indicators remained within the range of ENSO-neutral. On Sept. 14, the NOAA Climate Prediction Center (CPC) observed that oceanic and atmospheric conditions were shifting towards La Niña, with a 55- to 60-percent chance of a La Niña event in winter 2017-2018. On Sept. 21, the International Research Institute for Climate and Society (IRI) and CPC identified cool oceanic conditions and that “La Niña odds edge out neutral” over winter 2017-2018. The North American Multi-Model Ensemble (NMME) is ENSO-neutral as of September 2017 (Fig. 4), with a majority of the models predicting ENSO neutral or weak La Niña this winter.


Summary: In a slight shift from the last few months’ forecasts favoring ENSO-neutral conditions for this fall and winter, seasonal outlooks have turned more bullish on a weak La Niña event this fall. While many of the ENSO indicators remain within the range of neutral, oceanic indicators in particular have moved towards La Niña. What has caused the slight uptick in the likelihood of a 2017-2018 La Niña event that we noted in last month’s forecasts to become more pronounced? One answer is related to the way that expert forecasters respond to model outputs. The CPC/IRI outlook on Sept. 14 stated that “a majority of the models in the IRI/CPC suite of Niño-3.4 predictions favor ENSO-neutral through the Northern Hemisphere 2017-18 winter,” but they saw something in the NCEP Climate Forecast System (CFSv2) and North American Multi-Model Ensemble (NMME) that indicated a more rapid swing to La Niña conditions, and this influenced the overall assessment of an increasing chance of a weak La Niña this fall. It remains to be seen whether the winter will play out with ENSO-neutral or weak La Niña conditions. Given the warmer- and drier-than-average conditions associated with La Niña, this will be a closely watched phenomena going into the cool season of the Southwest, but neither scenario points toward particularly abundant winter precipitation.


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SW Climate Outlook Sept 2017 - Climate Summary

Thursday, September 21, 2017

Precipitation and Temperature: August precipitation ranged from much-below average to average across most of Arizona and New Mexico, except in eastern New Mexico where above-average to record-wettest conditions prevailed (Fig. 1a). August temperatures were average to much-above average in Arizona and most of New Mexico, with only the northeastern corner of New Mexico recording below-average temperatures (Fig. 1b). Temperatures during the June-July-August period have been mostly much-above average in Arizona and western New Mexico, and average to above average in eastern New Mexico (Fig. 2a). Year-to-date temperatures are persistently warmer than average, with much-above average and record-warmest conditions across nearly all of Arizona and New Mexico (Fig. 2b).

Monsoon Tracker: After a slow start in June and a record-wet July, precipitation in much of the Southwest has been mostly absent since early August. The high-pressure ridge that helped hold Hurricane Harvey in place over Houston kept moisture from circulating into the Southwest. The seasonal transition also played a role, as the mid-to-late monsoon period is typically much less conducive to widespread monsoon activity. This year, the late-season monsoon has been particularly dry, with very few storms and limited tropical storm activity that might otherwise help boost seasonal totals (Fig. 3).

Drought and Water Supply: Most of Arizona and New Mexico are currently designated as not experiencing widespread drought conditions on the most recent U.S. Drought Monitor (Fig. 4). An exception is the borderlands region of southern Arizona, which has designations of D0 (abnormally dry) and D1 (moderate drought) conditions, likely due to both short- and long-term precipitation deficits (Figs. 5a-5b). The monsoon is challenging when it comes to assessing drought impacts, as precipitation events have high intensity and great spatial variability. Furthermore, runoff and evaporation also limit the monsoon’s ability to mitigate drought conditions over large areas.

Health and Environmental Safety – Tropical Storms: Late September brings the period when regional atmospheric circulation patterns increase the likelihood that tropical storms could reach the Southwest. Looking at storms such as Norbert and Odile in 2014 and Octave in 1983 reveals the possible impacts these storms can have in terms of their effect on public perception and planning, along with their actual potential for extreme flood events. Coastal communities can see direct landfall impacts of tropical storms, but for Arizona and New Mexico, tropical storm activity most often acts as a moisture source for enhanced precipitation in late summer and early fall. These events can be relatively major for our region and warrant preparedness planning, although the possible impacts are of a different scale compared to major hurricane landfalls.

El Niño Southern Oscillation: Models and forecasts continue to indicate ENSO-neutral as one possible outcome, but recent forecasts have increased their probabilities of a La Niña event this fall. The CPC/IRI calls for a 55- to 60-percent chance of a La Niña developing based on numerous models shifting towards weak La Niña conditions (see ENSO Tracker for more details). La Niña events typically bring warmer- and drier-than-average conditions to the Southwest during the cool season, but a weak strength tempers some of those effects. Regardless, these developments are worth keeping an eye on as we head into the cool season given lingering concerns about long-term drought and water storage in the Southwest over the past 15 years.

Precipitation and Temperature Forecast: The three-month outlook for October through December calls for equal chances of above- or below-average precipitation in Arizona and New Mexico (Fig. 6, top), and increased chances of above-normal temperatures for the entire southwestern United States (Fig. 6, bottom).

In this Issue:

Beginning to Understand Climate Change in the Kaipara Catchment

Thursday, September 14, 2017

I’ve tagged along on environmental monitoring patrols, ridden in logging trucks with forestry workers, played cow wrangler on a dairy farm, photographed coastal erosion from the back of a four wheel drive that smelled of turkeys, and attended a conference on the wellbeing of eels. I’ve had conversations on boats and beaches, in fields and farmhouses, by lakes, in rivers, cars and marae (meeting houses). This is what happens when an anthropologist is on the case.

Figure 1: Here I am pictured on a river monitoring trip with Millan Ruka of Environment River Patrol-Aotearoa. Photo courtesy of D Clarke.

This summer, with the help of a CLIMAS Climate and Society Fellowship, I have had the chance to work with a fantastic group of people in the northern Kaipara Catchment of Aotearoa (New Zealand) to investigate the impacts of climate change on communities in the region. This research project grew out of conversations that were initiated in June 2016 between myself and the Integrated Kaipara Harbour Management Group (the IKHMG). The IKHMG is a Māori led, multi-stakeholder group working toward the restoration and collaborative, holistic management of the Kaipara Harbour and Catchment, that encompasses 640,000 hectares in the Auckland and Northland regions of Aotearoa. Alongside priorities such as regenerating native biodiversity and working towards the inclusion of mātauranga Māori (Māori knowledge) into management frameworks, the IKHMG is very interested in expanding its understanding of how climate change will affect communities throughout the catchment, and helping them to prepare for and adapt to these impacts. 

Climate change is predicted to bring increasing temperatures, less rainfall, more drought, intense rainfall events, pests and diseases, rising sea levels and ocean acidification to the Kaipara Catchment. Because the natural environment of the Kaipara is an integral part of many people’s identities, livelihoods and wellbeing, climate change has the potential to seriously affect communities in the area.

Figure 2: Map to show the location of the Kaipara Catchment

There is currently a lack of research into the socio-economic, health-based and cultural impacts of climate change in Aotearoa, and attention is generally more focused on higher-level climate change mitigation efforts than grassroots, community-led adaptation. Although a few studies do exist in this space, no such research has been conducted in the Kaipara, meaning that there are few guidelines or models for groups like the IKHMG to turn to. In order to begin to address this research gap I proposed last year to the IKHMG that I structure my Master’s research around climate change impacts and adaptation in the Kaipara Catchment. Since then, I have been working to bring this project to fruition: designing the research questions and protocols in collaboration with the IKHMG, drawing upon the expertise of CLIMAS personnel during planning meetings, taking a class in climate science, reading about climate change vulnerability and adaptation, and of course, making funding applications.

Between mid May and the end of July 2017, I conducted fieldwork in the northern part of the Kaipara Catchment. The research sought to assess community members’ understandings of climate change, their perceptions about how climate change may affect their lives, what they feel should be done to address these effects, and whether any opportunities are associated with impacts or adaptation efforts. Drawing on the invaluable experience that I have gained through working as a Research Associate with the University of Arizona’s Bureau of Applied Research in Anthropology, I engaged in many hours of structured observations, held 34 semi-structured interviews, and facilitated a community hui (interactive meeting) on climate change. These activities allowed me to gather information from a total of 76 people in the Kaipara. Because this research is, at its heart, about and for Kaipara communities, I made a point of inviting feedback on research questions, directions and outputs from both the IKHMG and community members with whom I spoke.

Figure 3: Participants at the Climate Change hui, held at the Otamatea Marae in June 2017.

Although I am only in the early stages of analyzing the data I gathered over the summer, I would like to briefly share some of the larger themes that have emerged.

In the Kaipara Catchment, many community members have concerns over issues such as freshwater and marine contamination, the decline of native biodiversity through land use change and pests and diseases, rural depopulation, lack of employment opportunities and financial security, and the loss of local knowledge systems, which have already placed pressure on community wellbeing. While climate change may not be at the forefront of many people’s minds, community members have noticed changes in weather patterns and environmental conditions, and for many, future climate change will interact with the issues mentioned above. In the Kaipara Catchment, the impacts of climate change will not happen in a vacuum; they will play out against a background of ongoing socio-political, historical, and environmental processes. 

My current understanding is that climate change will ultimately place further stress on community wellbeing, whether from the perspective of physical, mental and spiritual health, economic security, or socio-cultural identity.

To take just one example, many community members have concerns over the quality and abundance of kaimoana (seafood) such as shellfish in the Kaipara Harbour and coastal waters. These concerns are believed to be related to contamination of freshwater systems from colonial land use change, intensive agriculture, forestry, and sand extraction operations, and restriction of access due to private land ownership, overfishing and quota allocation. In recent years, worries over access to shellfish have intensified with higher than normal summer temperatures and increasing coastal erosion from sea level rise causing declining abundance and quality, and flooding of low lying roads making travel to shellfish beds difficult. In the future, more storms may lead to increasing contamination of shellfish with pollutants from higher in the Catchment, warmer temperatures may intensify the risk from pests and diseases, and ocean acidification may add further complications for shellfish survival.

Shellfish are an important resource for many coastal communities around the Kaipara. Many community members live in rural areas, where access to food stores, employment opportunities, and even unemployment benefits are restricted, meaning that shellfish is a key source of protein in the diet. The ability to share shellfish within the community, at hui, and with visiting whānau (family) and friends is also an important part of Māori culture, protocol, identity and knowledge systems that is already under strain. In addition, some community members’ livelihoods depend on small and larger scale aquaculture ventures. Climate change, then, may magnify existing concerns over wellbeing that are related to food security and physical health, the erosion of cultural identity, knowledge systems and protocol, and economic prosperity.


Figure 4: Sedimentation in the Kaipara Harbour is one of the ongoing threats to shellfish health that may interact with future climate change.

Figure 5: Coastal erosion presents another challenge to shellfish health in the Kaipara Harbour. Photo courtesy of Maree Jones.

Another suite of impacts relate to intensification of existing pressures on mental health and financial wellbeing. For example, many farm owners and workers in the Catchment already face challenges with isolation, stress, and a lack of financial security and independence. These may be increased with more droughts, floods, heavy rainfall events and pests and diseases in the future, as a result of needing to increase spending on infrastructure and farm resources, and potential loss of stock, crops, and employment.

Understanding the ways in which climate change will interact with existing processes and issues in the Kaipara is key in developing meaningful pathways to adaptation. Many people with whom I spoke emphasized that working to adapt to the impacts of climate change presents opportunities to address a wider network of issues – such as freshwater and Habour health, economic security, and lack of community representation in decision making – which are deeply intertwined with, and often at the heart of, the impacts that communities will experience. Successfully adapting to climate change in the Kaipara will involve engaging with these processes, to create environments and communities that can withstand the additional pressures that climate change may place on them.

Many interviewees see Catchment-level restoration as a key component in building the capacity to successfully respond to climate change impacts, such as the shellfish example discussed above. This will need to take place at a variety of levels and include a diversity of voices. Community, marae or school-level freshwater monitoring and environmental education programs, for example, may combine with collaborative ventures between communities, government and the dairy or forestry industry to encourage or legislate for riparian planting, exclusion of stock from waterways, and trapping sedimentation run-off. 

Figure 6: Encouraging Catchment restoration through activities such as riparian planting is a key part of working towards climate change adaptation for many community members.

Increasing farmer resilience to climate change is also an important theme that has emerged. Many interviewees suggested that mentoring programs may help farmers to alleviate mental health stress, and build their financial capacity to invest in infrastructure and withstand potential losses, while collaborative research and networking can assist farmers to experiment with new crops, stock, or techniques that stand up to changing climatic conditions.

Figure 7: Helping farmers build capacity to respond successfully to events like floods and droughts is another priority for communities in the Kaipara Catchment.

It has been heartening to witness the level of engagement of the IKHMG and other community members in this research project. Everyone that I have spoken to has been very generous with their time and knowledge, and I have been afforded some truly unique experiences by some of my interviewees. The research has even been featured in two local newspapers. You can read the stories here:,

Over the coming months, I will be working to write up my Master’s thesis, and produce a summary document for the IKHMG that will outline the main findings of the research. This document will be used by the IKHMG to help prepare communities for future climate change, by supporting adaptation measures. Although I have lived and breathed this research project for the past three months, I feel that I have only begun to scratch the surface in terms of understanding the complexities of climate change impacts and adaptation. In the coming months, I will be developing my PhD dissertation research proposal to continue working on climate change in the Kaipara in partnership with the IKHMG.

Figure8:  Beautiful Pouto Peninsula in the Kaipara Harbour

I am very grateful to CLIMAS, the Social and Behavioral Research Institute, the Graduate and Professional Student Council and the IKHMG for supporting this research. I would like to say a very special thanks to Willie Wright and Jane Worthington of the IKHMG, Shaun Awatere of Manaaki Whenua, Millan Ruka of Environment River Patrol-Aotearoa, and Dylan Clarke of Auckland Council for all their help, guidance and support along the way. Kaipara Ora!

You can read about the work of the IKHMG here:

Climate and Water Resources of the Chuska Mountains

Monday, September 11, 2017

In the fall of 2015, I began working with the Navajo Nation Department of Water Resources, Water Management Branch, to address water resource management questions they had for the Chuska Mountains. These mountains are the only native headwaters on the Navajo Nation, where water scarcity impacts Navajo tradition, culture and livelihood. Since our initial discussions, Water Management Branch staff and I have collaboratively developed guiding research questions about past changes in water and climate.

Our first field expeditions explored the landscape of the Chuska mountains so that I could better understand this unique place and its importance to the Navajo people (Photo 1). My guides were Carlee McClellan and Irving Brady from the Water Management Branch and Crystal Tully-Cordova and Lani Tsinijinni, both Navajo PhD students working on modern water in the Chuska Mountains.  They helped me stitch together an understanding of this hydroclimatic system, as well as help me visualize Navajo agricultural and traditional ties to the place.

My project is guided by the Navajo water managers’ interests and concerns. My research background drives our approach to investigating their questions. For this reason, I am following a two-prong strategy to try to answer questions of snow and surface water changes in the past. First, I am using tree rings and Navajo snow records to reconstruct Chuska snowpack prior to the last 30 years of instrumental records. Second, I am using satellite imagery to develop a baseline record of surface waters in the Chuskas for the last 30 years.


Photo 1  Navajo Water Management Branch field technicians Irving Brady and Ralphus Begay collect streamflow data for Whiskey Creek, Navajo Nation
Photo 2 Irving Brady demonstrates the use of a snow corer to sample snow pack. Snowpack snow water equivalent is determined from the weight of the snow sample in the tube. Staff at the Water Management Branch collect these data bi-monthly from January to April.

Gaining a Long-term View on the History of Snow

After initial analysis of the relationship between regional tree-rings and Chuska snow, it became clear that a strong connection exists between climate information contained in the rings and Chuska hydroclimate itself. This connection can be exploited to reconstruct past hydroclimate. However, to take advantage of the limited time period covered by the snow data, we concluded that we needed more current tree-ring records (Photo 2).

In January, buoyed by support from the Climate and Society Fellowship, I planned a field campaign to collect tree samples on the Mogollon Rim in northcentral Arizona. The goal of the field campaign was to update sites that showed a strong relationship with Navajo snow, and to supplement tree-ring records currently under development collected from the Chuskas. The Mogollon Rim experiences similar winter weather patterns as the Chuska Mountains. These patterns are reflected in regional SNOTEL and snow course site records. The existing Mogollon Rim tree-ring records were too short to cover the last three decades, an important hydroclimatic period because it overlaps with the Chuska snow data and because it captures a period of known hydroclimatic extremes in the region.

I felt excited anticipation about conducting fieldwork in higher elevations in winter, yet unsure about temperatures and snow depth. These uncertainties weighed on my mind as I traveled to Tucson to collect increment borers, sample straws, GPS units and, most importantly, my invaluable field crew Dr. Paul Sheppard and Alex Arizpe, from the Laboratory of Tree-Ring Research (Photo 3). Our destination was the area around the San Francisco Peaks, Arizona, where dendrochronologists collected tree-ring samples in the 1980’s. Our mission was to return to these notable sites and core new trees storing information for the last 30 years.  Our first stop was a pinion-juniper woodland near Sedona, Arizona, under overcast skies following a day of rain but no snow. The pinion trees were young and middle aged. This would be our only time in the more arid setting typically found with the pinion-juniper forests because the next three field sites were in the dry, park-like Ponderosa pine forest around Flagstaff, ARizona. We cored Ponderosa pine trees at Sunset Crater, Robinson Mountain nearby, and further to the west at Slate Mountain. Our final stop was snow-covered and at higher elevation in the cooler, denser Douglas fir forest of the San Francisco Peaks. There we found the snow and needed to post-hole in thigh-deep snow looking for promising trees to core.

Our two-day field campaign was successful! We returned to Tucson with 107 tree cores from 55 trees and 5 sites (Photo 4). Though I am still finalizing dates on the rings, at least one core dates back to 1636.  Mounting, sanding, counting, dating and developing an updated site chronology for each site is now nearly completed. Soon, these chronologies will be ready to use as potential predictors in a snowpack reconstruction model (Photo 5).


Photo 3 Becky Brice, Alex Arizpe, and Dr. Paul Sheppard stopping at Sunset Crater to collect tree cores, and photographs. 
Photo 4 We collected over 100 tree-ring samples from the Mogollon Rim, Arizona.  Dendrochronologists use increment borers to extract pencil-sized cores from trees (blue tubes). In the field, we place the fragile cores in rigid straws for transportation to the lab (white tubes). Once at the lab, we mount and sand each core for dating, measuring and analysis (wooden sticks at left).
Photo 5 Regional map of northeastern Arizona, including the Mogollon Rim near Flagstaff and the Chuska Mountains of the Navajo Nation. Blue dots show the location of snow course and SNOTEL sites. Purple dots show the location of tree-ring climate  sites used for this study. Green dots are existing tree-ring ecological sites collected by Christopher Guiterman.

Watersheds and Lakes of the Chuska Mountains

Surface waters in the Chuska mountains seem to be an indicator of hydroclimatic variability. The relationship between snowpack and surface waters is a pressing question for Navajo water managers, particularly if this relationship will help them better understand mountain runoff and water supply. However, streamflow records are limited in the Chuskas, and no lake level records exist for the naturally occurring lakes. In response to these basic data needs, my collaborators and I investigated approaches to quantify surface water changes.

To reconstruct a record of changing lake surface area, we decided to use satellite imagery and focus on three of the largest naturally occurring surface waters (Photo 6). Following my initial evaluation of lake levels in the Chuska Mountains, two goals emerged. The first goal was to have a way to accurately quantify lake area. I decided to walk the perimeter of at least one lake to ground-truth lake area estimated from satellites, versus lake area measured with GPS. The second goal was to visit the study area with a focus on watershed scale, location and orientation. How does the surface water run off these mountains, and then reside, anyway? I returned to the Navajo Nation in June to accompany Irving Brady, a Water Management Branch veteran of nearly 30 years, to view the watersheds. Irving has become an essential source of expertise and guidance for understanding the cultural landscape in this traditionally important mountain range, as well as for understanding the physical landscape itself. Data collected from this field trip is still being compiled and evaluated. I’m optimistic that it will help us further define and our understanding water resources in the Chuskas.

Photo 6 Toadlena Lake in the northcentral portion of the Chuska Mountains. Toadlena Lake is one of three lakes with estimated surface area using satellite imagery.

Ongoing Collaborations with Navajo Water Managers

Collaborating with the Navajo Nation has proven to be intellectually and professionally invigorating.  Partners at the Navajo Nation Department of Water Resources are supportive and have facilitated entry to essential locations in the otherwise hard-to-access Chuska range. Steep, loose and narrow forest roads necessitate an expertise unique to members of the community.

As a reciprocal effort, I have been actively sharing progress of my research through professional talks co-authored by collaborators at the Laboratory of Tree-Ring Research (LTRR), Dr. Christopher Guiterman and Dr. Connie Woodhouse, and Carlee McClellan at the Water Management Branch.  In April, I shared preliminary results during the University of Arizona’s Earth Week. Colleagues at the Laboratory of Tree-ring Research, enthusiastic about this study, introduced me to new ideas and potentially different approaches to my research.  I also shared these preliminary results at the Association of American Geographers Annual Meeting, Water Resources Specialty group in Boston. My colleagues in geography expanded my thinking even more broadly to thinking about the cultural landscape in combination with the physical place.

In May, I returned to meet with staff at the Navajo Water Management Branch to share what I’ve learned to this point. I developed a fact sheet to help illustrate progress on the research, to help facilitate information sharing, and to guide discussions about how the research is addressing the questions we initially chose to pursue.  Water managers were interested in these preliminary results, particularly the potential to gain a historic record of lake area changes for major surface waters in the Chuskas.

The first half of the 2017 Climate and Society Fellowship has proven to be wonderfully productive and fulfilling. I am looking forward to the next six months of generating results and use-inspired products.


Rainlog Climate Summary – August 2017

Tuesday, September 5, 2017

After an exceptionally wet July for many areas across Arizona, monsoon storm activity slowed down to a crawl leading to unusually dry conditions over the past month. August is typically the wettest month during the summer monsoon season in Arizona and the lack of thunderstorm activity stands out against the frequent and heavy activity that characterized much of the month of July. There were three days in August where no rainfall fell anywhere in Arizona (August 8th, 16th, and 18th), a strange and unusual occurrence in the heart of the monsoon season. The long-lived surge of moisture from the Gulf of California and reasonably favorable position of the upper level high pressure system that supported the frequent thunderstorm activity in July broke down in early August leading to much less favorable conditions for monsoon activity. The upper level high retreated south into Mexico ushering in drying upper level winds from the southwest and suppressing much of the thunderstorm activity across the state. Some higher elevation areas have been able to fire off afternoon thunderstorms on a handful of days in August, but most lower elevation areas have been left out of the action.

The overnight period of August 12th into the morning on the 13th was one of the heavier, widespread rain events that occurred during the month. Tropical Storm Jova passed west of Baja California around this time helping to push a slug of moisture up into southern Arizona. This provided the fuel for an outbreak of heavy thunderstorm activity in the overnight hours on the August 12th. Rainloggers in the Tucson metro area reported widespread amounts in excess of 1” with a handful of reports above 2.5”. Reports of daily totals in excess of 1” extended from southeast Arizona (Bisbee, Douglas, Sierra Vista) up through Phoenix and as far north as Prescott with this event.  

Overall, August precipitation totals look bleak across much of Arizona with respect to average levels. Some isolated areas have received average to above-average August totals, but most of Arizona has observed less than 75% of average with some locations (far northeast and parts of central AZ) seeing less 25% of their typical average total August precipitation. The monsoon season typically winds down through the first couple weeks of September, but the threat of tropical storms and associated moisture will keep the prospect of additional precipitation alive for this season.