Drought Information Statement for Arizona & SE California - Updated October 24, 2021

Monsoon 2021 Ends but Provides More Localized Drought Improvement

Updated on Sunday, October 24, 2021

Summary:

Although storm activity has waned since the middle of September, widespread heavy rainfall was common in July and August resulting in many parts of Arizona experiencing one of their wettest monsoons on record. While most areas enjoyed this beneficial wet weather, some communities along the Colorado River, northeast and north-central Arizona, as well as parts SE California missed out on the most prolific storms and rainfall. Nevertheless, rainfall amounts around the region have been so abundant that 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 as a result of this unusually wet monsoon. However, long term drought impacting hydrologic stability still exists across the Southwest region as a whole. 

Local Area Affected:

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

Extreme Drought (D3) - part of SE California

In SE California: very small part of eastern Riverside County

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

In Arizona: northern La Paz County

In SE California: eastern Riverside County

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

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

In SE California: Imperial County

Abnormally Dry (D0) - south-central and southwest Arizona

In Arizona: southern Yuma County, southern Maricopa, southern Pinal, and northern Gila counties

Local Climatology:

Below are precipitation totals since the beginning of the 2021 Calendar Year from selected locations across Arizona and southeast California.

Monsoon rainfall resulted in one of the wetter summer seasons for the southern half of Arizona.  In northern Arizona and the Upper Colorado basin, long term 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 experienced substantial responses from the repeated heavy rainfall events this summer. However, extended drier periods since the middle of September have resulted in some streams falling back to minimal flow. The more highly regulated larger rivers mostly remain in a near normal flow rates due to continual management efforts.

Rainfall earlier in the summer helped replenish soil moisture across much of the Salt/Verde basin, then periods of heavier rain later during the monsoon actually resulted in reservoir inflow. It`s common to see minor bumps in reservoir levels during the monsoon, but the larger increases in reservoir storage this monsoon is not
often experienced. In fact, inflow to Salt/Verde reservoirs this past monsoon was the 2nd greatest on record. 

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:

Only 5% of the Arizona range and pasture land rated as poor to very poor in mid September and October versus 57% in August and 78% in July. Widespread beneficial monsoon rainfall helped alleviate the most severe impacts for ranchers. In addition to forage growth,
stock ponds refilled in many areas.

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 another round of improvements across much of Arizona as heavy rainfall over the summer has contributed to lessening drought. The worst PDSI measure continues to be spread over northeast 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 a spring season of unusually dry fuels and expansive wildfire coverage, persistent and beneficial rainfall amounts abruptly ended the fire season in early summer. However, this abundant monsoon rain fed a new crop of grass growth which will likely become the fuel
next spring when fire season reemerges.  

As drier weather has been more prevalent in September and October, 100-hour dead fuel moisture has fallen below 10% after surging above 16% range in much of Arizona in August. Similarly, 10-hour dead fine fuels have languished between 5-8% across lower elevation locations, and upwards of 7-10% at higher terrain locations of central Arizona. 

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 Oct 31-Nov 6 period calls for better chances of above average temperatures and best odds for below normal rainfall. The 90 day outlook for the period November 2021 through January 2022 indicates better chances for above average temperatures and enhanced odds for below normal precipitation. 

While the tropical Pacific was ENSO neutral through the summer, sea surface temperatures have cooled again this fall and another La Nina episode has officially begun. There is approximately a 90% chance this La Nina will persist throughout the entire winter 2021-22 and into the spring season. La Nina winters in the Southwest historically favor below normal precipitation. 

. 

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/