Drought Information Statement for Arizona and SE California - September 11 2020

Severe to Extreme Drought Rapidly

Emerges Across the Region as Monsoon

Rainfall Fails to Deliver

Updated on Friday, September 11, 2020

Summary:

After fairly good winter and early spring precipitation, monsoon rainfall across the region has been much below normal. Many locations are experiencing one of their driest monsoon seasons on record, and now that is feeding back into top 10 driest year-to-date deficits. Aside from below normal precipitation, exacerbating the drought is record warmth this summer where many locations are setting all-time monthly and seasonal records. This resulting enhanced evapotranspiration is acting as a multiplier effect on short term drought impacts, and has aided in the rapid succession towards extreme drought. More prolific rainfall in the next month will be needed to improve drought conditions before the end of the monsoon and entry into the drier autumn season.

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 Severe to Extreme drought in much of Arizona the past couple months, but only minor degradation in SE California.  Moderate drought conditions exist in portions of Arizona where winter and spring precipitation was abundant and impacts thus far have been limited.  

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

In Arizona: eastern Maricopa, Pinal, and Gila counties

Severe Drought (D2) -  parts of south-central and southwest Arizona 

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

Moderate Drought (D1) -  parts of southwest Arizona 

In Arizona: central La Paz, and Yuma counties

Local Climatology:

Below are water year precipitation totals since October 2019 and totals
since the beginning of 2020 from selected locations across Arizona and
southeast California:

Aside from the fact monsoon rainfall has been paltry at best over most of the area, drought conditions have grown quicker as a result of extreme temperatures. The majority of Arizona (and a good deal of the entire Southwest) is experiencing an abnormally warm year, and the hottest summer months have set expansive records. 

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 June 24, 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 monsoon rainfall. Many of these small streams are flowing at or near record low levels for this time of year, especially in the east central parts of the state. The more highly regulated rivers remain in a near normal flow rates due to ongoing management efforts.

Due to good precipitation over the last 2 winters, reservoirs are actually above levels seen in the past several years. Monsoon rainfall typically does little to influence reservoir storage, however the lack of rain combined with record heat is likely creating extremely dry soils. As a result, future runoff could be negatively impacted even with average cool season precipitation. 

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 monsoon rainfall, range land and pasture conditions have shown rapid deterioration. 60% of the pasture and range land is rated poor or very poor compared to just 39% at this time last year. 

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 to High category for the entire area

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

Palmer drought severity index (PDSI):
The current weekly PDSI shows deterioration across the northern parts of Arizona due to a lack of rainfall over the past 4-5 months. More moist conditions are still recorded in southwest Arizona and southeast California as a holdover from the wet wet late winter and spring season.

After a fairly wet period at the beginning of the year spurred ample growth of fine 1 and 10-hour fuels along with some 100-hour fuels in lower elevations, very hot and dry weather has cured these fuels substantially. The larger 100-hour deal fuel moisture is under 10% for much of the state while finer 10-hour dead fuels were mostly under 6%.

Typically late in the monsoon season, these finer fuels would have been moistened by periodic rainfall. However with little rainfall this year, these finer fuels are still ripe for burning and the Arizona wildfire season has extended well beyond what is typical. Unless a burst of rainfall occurs before the monsoon ends, wildfire season may extend well in the fall before the much cooler winter weather arrives. 

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 Sept 18-24 period calls for better chances of above average temperatures and slightly enhanced odds for below average rainfall. The 90 day outlook for the period October through December 2020 indicates much better chances for above average temperatures and nearly equal odds for above, below, or near normal precipitation. 

ENSO had been maintaining a neutral state during the monsoon season, and really had no influence on the drier than normal weather. However, we are quickly transitioning into a La Nina episode which means a seasonal cooling of the equatorial Pacific waters. This La Nina should peak during the middle of the winter, and could reach a moderate category. The winter season during La Nina is strongly weighted towards near to below normal precipitation across the Southwest. Thus, odds are definitely tilted towards drier weather persisting, and probably little if any improvement to drought conditions in the next several months. 

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/