Drought Information Statement for Arizona & SE California - Updated August 21, 2021

Widespread Heavy Monsoon Rains Yield Significant Drought Improvement

Updated on Saturday, August 21, 2021

Summary:

 The 2021 monsoon circulation pattern has remained quite favorable for repeated, frequent showers and thunderstorms for the majority of the summer. Numerous rounds of widespread storms with heavy rainfall have been common since the end of July resulting in many parts of Arizona experiencing their wettest monsoon in decades. In fact, a few locations recorded their wettest July on record and now are flirting with all-time monsoon records. While most areas have been enjoying this beneficial wet weather, some areas of northeast and north-central Arizona as well as around El Centro in SE California have missed out on the better rainfall. Nevertheless, rainfall amounts around the region has been so abundant that soils have become saturated and excess runoff has resulted in local reservoir inflow. The most serious short term drought impacts in relation to ranching efforts, wildfire, and forest and wildlife health have been significantly reduced, though long term drought impacting hydrologic stability still exists.  

Local Area Affected:

The National Drought Monitor depicts substantial improvements in drought measures across Arizona and SE California.

Extreme Drought (D3) - part of far western Arizona and SE California

In Arizona: northwest La Paz County

In SE California: much of eastern Riverside County

Severe Drought (D2) -  parts of southwest Arizona and SE California

In Arizona: La Paz and small part of Maricopa counties

In SE California: part of Riverside and northern Imperial counties

Moderate Drought (D1) - south-central and southwest Arizona and SE California

In Arizona: Gila, Pinal, most of Maricopa, southern La Paz and northern Yuma counties

In SE California: southern Imperial County

Abnormally Dry (D0) - southwest Arizona

In Arizona: far southern Yuma County

Local Climatology:

Below are precipitation totals since the beginning of the 2020-21 Water Year from selected locations across Arizona and southeast California (Please note Normals have been adjusted to reflect the new 1991-2020 official climate period):

In addition to the long term precipitation deficit, drought conditions worsened and expanded more rapidly as a result of extreme temperatures. While precipitation deficits have decreased somewhat in the past 2 months, long term regional shortages still exists. Record or near record heat over the past year have only exacerbated drought intensity though extra evapotranspiration. 

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 May 11, 2021. This recommendation is based on long term precipitation deficits and impacts experienced 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 seen rapid and substantial responses from the repeated heavy rainfall events this summer. In fact, many unregulated smaller streams are flowing well above, and even near record levels this August. The more highly regulated larger rivers remain in a near normal flow rates due to continual management efforts.

After the abnormally dry winter, total system runoff on the Salt/Verde basin this past spring was the historical 2nd lowest recorded. Early monsoon rainfall helped replenish soil moisture in many locations, then periods of heavier rain over the past month
actually resulted in reservoir inflow. It`s common to see minor bumps in reservoir levels during the monsoon, but the notable increases in reservoir storage this monsoon is not often experienced.

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:

57% of the Arizona range and pasture land rated as poor to very poor compared to 78% last month, but just 42% at this time last August and the 5-year average of 40%. After a prolonged period of excessively dry conditions with natural forage mostly absent and
supplemental feed a necessity, widespread beneficial rainfall has
helped alleviate the most severe impacts for ranchers. Stock ponds
have refilled in most areas and even an extended period of below
normal temperatures have been aiding livestock health.

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: Low to Moderate category across the region

The current KDBI: Southwest Arizona and southeast California: Ranging from Extreme lower elevations of SE California and southwest Arizona and Low in eastern Arizona.

Palmer drought severity index (PDSI):
The current weekly PDSI shows very large improvements across southern Arizona as recent heavy rainfall has contributed to lessening drought. The worst PDSI measure continues to be spread over northern Arizona and SE California where monsoon rainfall has been more spotty and drier than normal conditions have been prevalent over the past several years.  

After very hot, dry, and breezy weather over the spring produced a crop of unusually dry fuels, wildfire coverage started outpacing last year with extensive amounts of burned area. A persistently favorable monsoon circulation pattern brought thick moisture and repeated rounds of rainfall to the region abruptly ending the fire season in early summer. However because of the amount of area burned and intensity of the fire activity, flooding and debris flows from these burned areas have become tremendous hazards for downstream communities. 

With the recent surge of better moisture and periodic rainfall, 100-hour dead fuel moisture has improved above 16% range in the eastern 2/3rds of Arizona, while still hovering in a 6-10% range to the west. Similarly, 10-hour dead fine fuels have improved over the eastern parts of Arizona where values were in a 7-15% range. To the west, values were nearly steady in a 5-6% range. 

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 August 28-Sept 3 period calls for better chances of above average temperatures and best odds for near normal rainfall. The 90 day outlook for the period September through November 2021 indicates better chances for above average temperatures and enhanced odds for below normal precipitation. 

La Nina peaked in the tropical Pacific last winter with sea surface temperatures now hovering around average. The pattern has settled into a neutral state, and will remain as such into the autumn. However, there is about a 70% chance of La Nina returning again in
the fall/winter 2021-22 with odds favoring another winter season of below normal precipitation throughout the region.
 

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/