Drought Information Statement for Arizona & SE California - Updated November 20, 2020

Exceptional Drought Continues

to Expand

Updated on Friday, November 20, 2020

Summary:

After the driest monsoon on record for the region, autumn precipitation has been just as lacking resulting in further expansion of extreme and exceptional drought conditions. For some locations, it`s been over 6 months since the last measurable rainfall. In addition to this lack of precipitation, record heat has been a recurring theme. Well above normal temperatures have persisted beyond the summer with communities experiencing unusual heat well into the fall. This has resulted in increased evapotranspiration helping exacerbating short term drought impacts, and expansion of the rare exceptional drought measure. More frequent and heavier precipitation events will be needed this winter to begin to make a dent into the deficits and help alleviate drought impacts.

Much of the drought impacts have been focused in short term influences such as forage for ranchers, water availability for land based wildlife, and small stream flow for aquatic wildlife. Recent wetness during the winter seasons has resulted in adequate long term hydrologic stability. 

Local Area Affected:

The National Drought Monitor depicts growth in Extreme and Exceptional drought in much of Arizona the past couple months, and minor degradation in SE California.  Moderate drought conditions only still exist in portions of southwest Arizona where winter and spring precipitation was abundant and impacts thus far have been limited.  

Exceptional Drought (D4) - part of south-central Arizona

In Arizona: eastern Maricopa, southern Gila, and Pinal counties 

Extreme Drought (D3) - across much of central, southern, and eastern Arizona

In Arizona: central Maricopa, far western Pinal, and northern Gila counties

Severe Drought (D2) -  parts of southwest Arizona 

In Arizona: western Maricopa, eastern La Paz, and eastern Yuma counties

Moderate Drought (D1) -  parts of southwest Arizona and SE California

In Arizona: western La Paz, and Yuma counties

In SE California: Imperial and eastern Riverside counties

Local Climatology:

Below are precipitation totals since the beginning of 2020 from selected locations across Arizona and southeast California:

Aside from very limited rainfall amounts and coverage, drought conditions have grown more rapidly as a result of extreme temperatures. The majority of Arizona and the entire Southwest is experiencing an abnormally warm year. The past 6 months have been record breaking in all possible respects, and now the persistent warmth is showing up as all-time heat even in the annual statistics. 

The U.S. Drought Monitor is a weekly collaborative effort between a number of federal agencies including NOAA/NWS, U.S. Department of Agriculture and the National Drought Mitigation Center. Details and explanations of the Drought Monitor can found at the web site:

http://droughtmonitor.unl.edu/ 

The categories of drought are defined as follows:

Abnormally Dry (D0) - Going into drought: short-term dryness slowing planting, growth of crops or pastures; fire risk above average. Coming out of drought: some lingering water deficits; pastures or crops not fully recovered.

Moderate Drought (D1) - Some damage to crops, pastures; fire risk high; streams, reservoirs, or wells low, some water shortages developing or imminent, voluntary water use restrictions requested.

Severe Drought (D2) - Crop or pasture losses likely; fire risk very high; water shortages common; water restrictions imposed.

Extreme Drought (D3) - Major crop/pasture losses; extreme fire danger; widespread water shortages or restrictions.

Exceptional Drought (D4) - Exceptional and widespread crop/pasture losses; exceptional fire risk; shortages of water in reservoirs, streams, and wells, creating water emergencies.

State and Local Actions:

A Drought Emergency Declaration remains in effect for the state of Arizona as signed by the governor in accordance with the Arizona Drought Preparedness Plan. The continuation of this Drought Emergency has been recommended by the Drought Interagency Coordinating Group in their bi-annual meeting on November 10, 2020. This recommendation is based on long term precipitation deficits, along with ongoing negative impacts across the state.

Additional information concerning the drought in Arizona can be obtained via the Arizona Department of Water Resources web site at:

https://new.azwater.gov/drought

Additional information concerning the drought in California can be obtained via the California Department of Water Resources web site at:

http://www.water.ca.gov/waterconditions

River, Stream Flow, and Reservoir Conditions:

Smaller streams throughout Arizona have been suffering as a result of the lack of rainfall the past 6 months. Many of these small streams are flowing at or near record low levels for this time of year, especially in the eastern parts of the state. The more highly regulated larger rivers remain in a near normal flow rates due to ongoing management efforts.

Due to ample precipitation over the last 2 winters, reservoirs are actually above levels seen in the past several years. Autumn rainfall typically only has minor influence on short term reservoir storage, however the lack of rain over the past 6 months combined with record heat is likely creating extremely dry soils. As a result, future runoff in the spring could be negatively impacted even if average winter precipitation were to materialize.

Hourly and forecast river stages out to 90 days can be found at the National Weather Service's (NWS) Advanced Hydrologic Prediction Service (AHPS) web page:

http://water.weather.gov/ahps2/index.php?wfo=psr

Additional Current stream and river stages may be viewed at the following USGS Web Site:

http://waterwatch.usgs.gov/

Agriculture Impacts:

With extreme heat and lack of monsoon rainfall, impacts have been substantial on area ranchers. These impacts have included need for increased water hauling, depleted stock ponds, distressed vegetation, and loss of forage acreage. As as result, livestock on regional ranches have suffered the greatest impacts. With little rainfall in the past 6 months, range land and pasture conditions have shown steady deterioration with 85% of Arizona rated as poor or very poor. 

For additional information on agriculture impacts may be viewed at the United States Department of Agriculture (USDA) National Agricultural Statistics Service NASS Web Site:

        https://www.nass.usda.gov/Statistics_by_State/
index.php

Fire Danger Hazards:

The National Fire Danger Rating: Moderate category for the entire area

The current KDBI: Southwest Arizona and southeast California: Ranging from Extreme in SE California and much of Arizona to High in some of the higher elevations of northern and eastern Arizona

Palmer drought severity index (PDSI):
The current weekly PDSI shows a nearly steady state over the past month. The worst PDSI measure remains in NE Arizona where drier than normal conditions have been most prevalent over the past several years. More moist conditions are still recorded in southwest Arizona and southeast California as a holdover from the wet late winter and spring season.

Ample precipitation at the beginning of the year spurred growth of fine 1 and 10-hour fuels along with some 100-hour fuels in lower elevations. However, very hot and dry weather cured these fuels substantially through the summer. Typically during the monsoon season, these finer fuels would have been moistened by periodic rainfall; and the cooler autumn weather completely ending any wildfire risk. However with very little rainfall this year and continued warm weather, these finer fuels are still capable of burning. 100-hour dead fuel moisture has increased back to above 6% while 10-hour fuels are a mixture of 3-6% - both measures drier than typical for late fall. 

The Keetch-Byram Drought Index (KBDI) is a drought index that is specifically related to fire potential. The KDBI is broken into four categories which indicate the susceptibility of ground fuels to fire danger. Below are the four categories and a brief description of each.

KBDI and Dead Fuel Moisture data can be found on the Wildland Fire Assessment System (WFAS) web site at:

http://www.wfas.net

Precipitation/Temperature Outlooks:

The 8-14 day temperature outlook for Nov 28-Dec 4 period calls for better chances of near average temperatures and elevated odds for below normal rainfall. The 90 day outlook for the period December 2020 through February 2021 indicates better chances for above average temperatures and enhanced odds for below normal precipitation. 

The tropical Pacific has settled into a La Nina condition, which will further strengthen and mature into winter. Conditions should not moderate back to a neutral state until the spring with La Nina likely reaching a moderate to strong category. While other factors contribute to the atmospheric pattern, drier than normal weather is strongly favored during these type of La Nina years. Current forecasts suggest around a 60% chance this winter as a whole will end up in this drier category, while the chance of a wetter than normal winter is only around 10%.  

For updated temperature and precipitation probabilities consult the following Climate Prediction Center (CPC) Web Sites:

8 to 14 Day Outlook:

http://www.cpc.ncep.noaa.gov/
products/predictions/814day/

30 Day Outlook:

http://www.cpc.ncep.noaa.gov
/products/predictions/30day/

90 Day Outlook:

http://www.cpc.ncep.noaa.gov/products
/predictions/long_range/seasonal.php?lead=01

Questions or Comments:

If you have any questions or comments about this information
please contact:

w-psr.webmaster@noaa.gov

Acknowledgements:

The Drought Monitor is a multi-agency effort involving NOAA’s National
Weather Service and National Centers for Environmental Information, 
the USDA, state and regional center climatologists and the national
drought mitigation center. Information for this statement has been gathered
from NWS and FAA observation sites, cooperative and volunteer observations,
USDAFS, the USDA and USGS.

Related Websites :

NWS - http://www.weather.gov/phoenix

CPC - http://www.cpc.ncep.noaa.gov

Drought Monitor - http://droughtmonitor.unl.edu/

USGS - http://waterwatch.usgs.gov/

COE - http://www.spk.usace.army.mil/