Drought Information for Arizona and Southeast California (Updated October 26, 2018)

SUBSTANTIAL DROUGHT IMPROVEMENTS AS A RESULT FROM RECORD RAINFALL ACROSS MUCH OF THE REGION IN OCTOBER

Updated on Friday, October 26, 2018 - Mark O'Malley

Summary:

Abundant moisture from a remnant Pacific hurricane and a persistent, favorable weather pattern yielded several heavy rainfall events across much of the Southwest United States during the first half of October. Record rainfall has been noted across much of central Arizona with Phoenix experiencing its wettest October on record (since 1896) and its 3rd wettest month (any month) ever. As a result, substantial improvements in the Drought Monitor have been made in the past couple weeks.

The heavy rains have helped both short term rangeland conditions and streamflow through much of Arizona. Soil moisture profiles and fire weather conditions have correspondingly improved. However, improvements to longer term water resources will require additional winter rain and snow given the prolonged regional drought.

Local Area Affected:

The National Drought Monitor depicts substantial drought improvement over Arizona this month, with modest improvements in SE California. Vast improvements from Extreme and Severe Drought to only Moderate Drought and Abnormally Dry conditions occurred over much of Arizona. Severe to Extreme drought persists across southwest Arizona and far southeast California though some improvement has been noted in the past month. 

Extreme Drought (D3) - parts of Southeast California

In California: much of Imperial County

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

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

In California: central Riverside and far eastern Imperial counties

Moderate Drought (D1) -  parts of south-central Arizona and southeast California

In Arizona: southern Gila, much of Pinal and portions of Maricopa counties

In California: eastern Riverside County

Abnormally Dry (D0) -  parts of south-central Arizona 

In Arizona: western Pinal and central Maricopa counties

Local Climatology:

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

Rainfall during the first part of October has been impressive with many locations setting records for the month of October. This has also pushed year-to-date percentage near of above 100% for much of central AZ

October 2018 Rainfall	2018 Year-to-Date Precipitation

The long term drought conditions have been exacerbated by the fact that the majority of Arizona (and a good deal of the entire Southwest) experienced its warmest Water Year (Oct 1st-Sept 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 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. 

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 rivers and streams have responded to the excessive October rainfall, though there is still a wide range in flows. Some smaller streams have already fallen back below normal, however most waterways are flowing at or above average for this time of year. 

Reservoir levels remain well below levels at the same time last year, and similar to levels in 2016. Spring runoff was near record low levels and the recent heavy rainfall has only marginally helped inflow. Better winter rain and snow will be needed to see better recharge heading into next spring. 

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:

Extensive October rainfall was beginning to aid in range land and pasture condition improvements though full recovery may be hindered by the longer term drought. Reports from around the region indicate stock ponds are beginning to refill. However, 58% of the pasture and range land still is rated poor or very poor. Just one month ago, around 65% of range land was rated poor or very poor versus just 13% 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 High in SE California and much of SW Arizona to Moderate central Arizona and the higher elevations north and east of Phoenix

Palmer drought severity index (PDSI):
The current weekly PDSI shows substantial improvements across allof Arizona resulting from several period of heavy rain during the first part of October. SE California continues to experience the most prolonged dryness and Severe Drought (-3.0 to -3.9) conditions continue valid per this PDSI measure. Central Arizona has experienced the most excessive rain and areas that were in Moderate to Severe Drought just a month ago are now categorized as Very Moist.

Recent rainfall and larger increases in humidity levels with the cooler fall weather have allowed 100-hour dead fuel moisture values to improve above 10% (and even above 15%) for much of the higher elevation areas of central and eastern Arizona. Smaller sized 10-hour dead fuel moisture values have also increased above 7% recently in much of Arizona. Fuel moisture values were still lagging over far western Arizona and SE California where rainfall has not been as heavy. 

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 Nov 4-10 period calls for slightly better chances of above average temperatures and the best chance of near average rainfall. The 30 day outlook for November 2018 (not shown) indicates better chances for above average temperatures and a very slight chance of above average precipitation. The 90 day outlook for the period November 2018 through January 2019 indicates better chances for above average temperatures and slightly enhanced odds of above average precipitation. 

ENSO has been maintaining a neutral state, however we are transitioning to an El Nino episode and confidence is now high that equatorial Pacific sea surface temperatures will reach El Nino thresholds later this fall. El Nino should peak during the middle of the winter, but only reach a weak and maybe briefly moderate category. While many other factors contribute to the atmospheric circulation pattern, there may be a slight tilting of the odds towards wetter conditions later in the year due to this El Nino cycle. 

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/