Drought Information for Arizona and Southeast California (Updated June 21, 2018)

EXTREME TO EXCEPTIONAL DROUGHT PERSISTS AND EXPANDS HEADING INTO THE MONSOON SEASON

Updated on Thursday, June 21, 2018 - Mark O'Malley

Summary:

Not surprisingly given the typically dry and hot spring season, there has been no relief to drought conditions across the Southwest region during the past month. Precipitation amounts for the Water Year 2017-18 (since Oct 1st) have been paltry with many locations in central and northern Arizona, as well as southeast California placing within the top 5 driest ever recorded. 

Regional precipitation deficits remain substantial with a growing list of impacts. Ranchers have reported little to no forage for livestock with stock ponds completely empty. Fire season began unusually early over the higher terrain necessitating the closure of many state and federal recreational lands. While still not yet critical, water resources are a concern given the lack of winter snow. As a result, extreme and exceptional drought conditions have continued to expand during the past month. 

Local Area Affected:

The National Drought Monitor depicts worsening drought conditions over the region in the past several months. Extreme and Exceptional drought conditions still continue to expand over a large part of Arizona. 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. 

Exceptional Drought (D4) - across parts of central Arizona

In Arizona: far eastern Maricopa and part of Gila counties

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

In Arizona: western Maricopa, northern Pinal, southern 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

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:

           (Percent of normal precipitation since October 1st)

The drought conditions have been exacerbated by the fact that the majority of Arizona (and a good deal of the entire Southwest) is experiencing its warmest Water Year (Oct 1st-May 31st) 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 May 29, 2018. 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 extreme drought conditions. Many state lands have been closed for public recreation due to the extreme fire threat.  

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 continue to flow at much below average rates with unusually low rain and snow amounts this Water Year. Many of these smaller rivers and stream are flowing below the 10th percentile for this time of year. The only exceptions have been larger regulated rivers, including much of the Colorado River, which remain in a near normal flow rates due to ongoing 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 was also far less than last year. Runoff has been 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 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 and many ranchers are selling off higher amounts of their herds this year.

Range land and pasture conditions have worsened substantially in the past couple months. 87% of the area pasture and range land has been rated poor or very poor. Only some recent rainfall has allowed some localized improvements. Just one month ago 90-100% of range land was rated poor or very poor versus just 31% 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 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 the entire Southwest region due to lack of rain and snow. The Extreme Drought (-4.0 or greater) category now covers all of Arizona and SE California. 

A recent brief spike in humidity levels and light rainfall has actually allowed 100-hour dead fuel moisture values to improve above 5% for much of central Arizona through SE California. Even better conditions are reported in eastern Arizona where values have risen above 10%. These improvements may begin to deteriorate again through the end of the month with hot, dry weather returning before the heart of the monsoon season arrives.

The smaller sized 10-hour dead fuel moisture values have also seen a modest improvement into a 3-4% range, but similarly could easily fall back into a 1-2% range in before the end of the month.

Wildfires have been more prevalent early in the spring season than is usual. However, preventative efforts such as closing large portions of state land along with fairly tranquil weather conditions have precluded a worse fire season so far. The region is currently near the seasonal peak of the wildfire season with the enhanced threat persisting the next couple weeks before deeper moisture and much more humid conditions overspread the region. 

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 June 28-July 4 period calls for better chances of above average temperatures and precipitation likely not too far from average (typical fairly minimal this early in the monsoon season). The 30 day outlook for July 2018 (not shown) indicates somewhat better chances for above average temperatures and above average precipitation. The 90 day outlook for the period July through September 2018 indicates much better chances for above average temperatures and slightly enhanced odds of above average precipitation. 

La Nina conditions have weakened fairly rapidly this spring and transitioned to neutral over the past month or so. This La Nina likely has exhibited some influence on the drier winter, however has had little to no impact on weather this late spring season. Based on some longer term model simulations,there is some evidence suggesting the monsoon season could be wetter than normal on the larger scale. However as is typical with summer thunderstorms, rainfall amounts can be highly variable over small distances. While evidence is growing that an El Nino phase will materialize by the end of the year, forecast uncertainty during this time of year is large regarding timing and magnitude of Pacific sea surface temperatures. 

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/