Drought Information for Arizona and Southeast California (Updated May 18, 2018)

DROUGHT SLOWLY WORSENS DURING THE DRIEST AND HOTTEST PART OF THE YEAR

Updated on Thursday, May 17, 2018 - Mark O'Malley

Summary:

There has been little to no drought relief across the entire Southwest region over the past month with only one weather system bringing spotty rain and snow. Precipitation amounts for the Water Year 2017-18 (since Oct 1st) have been paltry with many locations in Arizona sitting as one of the top 5 driest winters ever recorded. We have now entered into the drier spring season where little additional precipitation will fall until the summer monsoon, and any improvement to drought conditions should not be expected. 

Regional precipitation deficits remain substantial, especially with respect to high elevation snow. Impacts with respect to ranching and water resources have been steadily growing over the past several months. As a result, extreme drought conditions have continued to expand and some areas have worsened into the exceptional drought category over the past month. 

Local Area Affected:

The National Drought Monitor depicts slowly worsening drought conditions over the region in the past months. Extreme drought conditions still continue to expand over a large part of Arizona, and now pockets of Exceptional Drought are growing over areas that have the greatest precipitation deficits. Severe drought conditions exist much of the remainder Arizona, except the far northwest and southeast parts of the state where Moderate drought conditions exist. Extreme drought remains in parts of far southeast California with Severe drought holding firm through the rest of the southeast California deserts. 

Extreme Drought (D3) - across much of central, southern, and western Arizona, as well as Southeast California

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

In California: much of Imperial and far southeastern Riverside counties

Severe Drought (D2) -  southeast California

In California: far western Imperial and much of eastern Riverside counties

           (Percent of normal precipitation since October 1st)

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:

The drought conditions have been exacerbated by the fact that essentially the southern 2/3rds of Arizona (and a good deal of the entire Southwest) is experiencing its warmest Water Year (Oct 1st-Apr 30th) 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. In northeast Arizona, the Navajo Nation has issued an emergency drought declaration to deal with severe drought conditions. 

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:

Most smaller, unregulated rivers through the state of Arizona are flowing at much below average rates with unusually low rain or snow amounts over the past 6 months or more. Many of these smaller rivers and stream are flowing below the 10th percentile for this time of year. The only real exception has been larger regulated rivers, including much of the Colorado River, which remain in a near normal flow rates due to management efforts.

Reservoir levels at this point of the year have fallen well below levels at the same time last year. The mountain snow pack above these reservoirs is also far less than last year with the snow season just about over. Runoff will be well below average for the remainder of the spring (near record low levels) and additional reservoir re-charge will be minimal 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 increased water hauling necessary for farmers and ranchers, distressed vegetation, and loss of forage acreage. Most new forage areas are completely absent this year, and there have been reports in NW Arizona of evergreens dying due to lack of moisture. Reports around the state indicate stock tank water has now become nearly non-existent requiring extensive water hauling. Livestock on regional ranches have suffered the greatest impacts from drought conditions and many ranchers are considering selling off higher amounts of their herds this spring.

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. 100% of the area pasture and range land has been rated poor or very poor versus 86% one month ago and just 15% 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: High to Very High, and even occasionally Extreme category for the entire area

The current KDBI: Southwest Arizona and southeast California:

Ranging from Extreme in SE California and  much of SW and central Arizona to High towards higher elevations of central and eastern Arizona.

Palmer drought severity index (PDSI):
The current weekly PDSI shows continued long term deterioration across much of the region due to lack of rain and snow. The Extreme Drought category now covers almost all of Arizona and SE California with the exception of  Moderate (-2.0 to -2.9) Drought still holding over SW Arizona. 

Abnormally dry conditions have pushed 100-hour dead fuel moisture values down below 5% for almost all of the Southwest except for some higher elevation areas of northern Arizona and the more sparsely covered lower desert of SE California. 

The smaller sized 10-hour dead fuel moisture values have fallen into the worst 1-2% category over the SE quarter of Arizona. The remainder of the area falls in a 3-4% range. 

These fuel moisture values are more indicative of values typically seen during the height of the fire season in the middle of June versus May. Not surprisingly, wildfires have been more prevalent early this spring than is usual. The combination of these increasingly dry fuels may lead to enhanced fire behavior in the future should dry and windy weather conditions develop before heart of monsoon season 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 May 25-May 31 period calls for better chances of above average temperatures and precipitation likely not too far from average (which is typically zero anyways). The 30 day outlook for June 2018 (not shown) indicates better chances for above average temperatures and equal chances for above, below, or near average precipitation (which is close to nothing for much of the state anyways). The 90 day outlook for the period June through August 2018 indicates much better chances for above average temperatures and equal chances of above, below, or near average precipitation. 

La Nina conditions have weakened fairly rapidly this spring; and a transition to neutral conditions is now occurring. This La Nina likely has exhibited some influence on the drier winter, however will exhibit little influence for the remainder of the spring as the signal wanes. Once the shift to neutral conditions occurs, any predictable influence of this cycle will be negligible. There is little to no evidence suggesting whether the upcoming summer monsoon season would be wetter or drier than normal. While there may be some chance of entering an El Nino phase by the end of the year, forecast uncertainty during this time of year is notoriously high.

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/