Drought Information Statement for Arizona and Southeast California

DROUGHT EXPANDING AND INTENSIFYING ACROSS THE REGION

Updated on Friday, February 16, 2018 - Mark O'Malley

Summary:

After monsoon rains ended abnormally early, a persistent dry pattern locked into the Southwest over the autumn season and has only occasionally given up a hold on the region. Precipitation amounts for the Water Year 2017-18 have been paltry with many higher elevation locations barely recording much snow yet this winter. This is typically a wet period for the region, especially across the mountains of northern and eastern Arizona where snowpack is accumulated and refills reservoirs in the spring.

Statewide precipitation deficits are now growing appreciably, especially with respect to high elevation snow; and it appears unlikely that recovery to near normal levels will occur 
before the dry spring season begins. As a result, drought conditions have grown rapidly since the beginning of the year with severe levels covering much of the state, and extreme drought  already developing. 

Local Area Affected:

The National Drought Monitor has depicted a worsening in drought conditions over the region in the past several months. Extreme drought conditions now prevail over a small part of eastern and southern Arizona. Severe drought conditions exist much of the remainder Arizona, except the far western parts of the state where Moderate drought conditions exist. Moderate drought also exists over all of southeast California.

Severe Drought (D2) - across central and southern Arizona

In Arizona: Eastern Maricopa, Pinal, Gila, and much of Yuma counties

Moderate Drought (D1) - across western Arizona and southeast

California.

In Arizona: Western Maricopa, La Paz, and part of Yuma counties

In California: Imperial and Riverside counties

Local Climatology:

Below are water year precipitation totals since October 2017 and totals
since the beginning of 2018 from selected locations across Arizona and
southeast California:

Making the lack of rain worse has been the unseasonably warm temperatures this winter. Phoenix has barely experienced temperatures below 40 degrees, and reaching near record levels has been almost as common as being near normal. 

In fact, the majority of the state of Arizona will likely end the winter as the warmest in recorded history (since 1895). 

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 16, 2017. 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, unregulated rivers through the state of Arizona are now flowing at much below average rates with unusually limited rain or snow during the past 5 month. Larger regulated rivers, including much of the Colorado River, remain in a near to normal flow rate due to management efforts.

Reservoir levels at this point of the year are slightly lower than the same time last year. However, the amount of snow pack in the mountains above the reservoirs is far less than last year, and it is unlikely that additional precipitation the remainder of this winter season will reach anywhere near the seasonal normal. Several larger storm systems will be needed before the middle of spring to have any sizable effect on reservoir levels later this year. 

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 prolonged drought conditions, impacts have included periodic water hauling necessary for farmers and ranchers, distressed vegetation, and loss  of forage acreage. Livestock on regional ranches have suffered the greatest impacts from drought conditions. Range land and pasture conditions have worsened substantially in the past couple months after monsoon rains stopped early and winter rain and snow have been lacking. 44% of the area pasture and range land has been rated poor or very poor versus just 22% 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: Low to Moderate category for the entire area

The current KDBI: Southwest Arizona and southeast California:

Ranging from Extreme in SE California and SW Arizona to Moderate to High towards central Arizona.

Palmer drought severity index (PDSI):
The current weekly PDSI shows steady deterioration across much of the region due to lack of rain and snow. The Extreme Drought category covers much of eastern Arizona with Severe (-3.0 to -3.9) Drought conditions encompass all of SE California, as well as central Arizona. Moderate (-2.0 to -2.9) Drought exists over all of NW through SW Arizona. 

Abnormally dry conditions have pushed 100-hour dead fuel moisture values into a 6-10% across most lower elevation locations with more moist conditions at higher terrain areas.

The smaller sized 10-hour dead fuel moisture values have fallen into a 5-6% range across the southeast parts of Arizona. Slightly better conditions exist elsewhere in the region. Further drying of these fine fuels will likely occur heading through the spring month. The combination of these increasingly dry finer fuels and favorably dry 100-hour fuels may lead to enhanced behavior in the future should dry and windy weather conditions develop later in the spring. 

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 February 23-March 1 period calls for better chances for below normal temperatures and above average precipitation. The 30 day outlook for March 2018 (not shown) indicates better chances for above average temperatures and essentially equal chances for above, below, or near average precipitation. The 90 day outlook for the period March through May 2018 indicates much better chances for above average temperatures and modestly better chances of below average precipitation. 

La Nina conditions are continuing this winter and early spring though a shift to neutral conditions should occur later in the spring and summer. This La Nina likely has exhibited some influence on the drier winter so far, and will continue to tilt the odds towards drier weather in the near future. Once the shift to more neutral conditions occur, the predictable influence of this La Nina cycle will wane. There is little to no evidence suggesting whether the upcoming summer monsoon season would be wetter or drier than normal. 

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:

Mark O’Malley
Climate and Drought Services
National Weather Service-Phoenix
Co-Chair Arizona Drought Monitoring and Technical Committee
mark.omalley@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/