October 2013

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Latest Monthly Assessment - The October Drought Outlook is based on initial conditions, short and medium range forecasts, the CPC monthly outlooks, and climatology. During September 2013, drought improvement and removal occurred across the Southwest, parts of the Great Plains, and along the Gulf Coast. Improvement and removal is expected for the lower Mississippi Valley and along the Texas Gulf Coast. Prospects for improvement decrease inland and persistence is forecast for the remainder of Texas and most of the Great Plains. Drought improvement and removal across parts of the northern Rockies, Midwest, and upper Mississippi Valley is based mostly on expected precipitation during the first week of October. Following major improvement during September, persistence is forecast across the remaining long-term drought areas of the Southwest. Recent heavy precipitation and climatology favor removal or improvement of drought across southwest Oregon and extreme northwest California. Precipitation typically does not increase significantly until after October across the remainder of California. Therefore, persistence is forecast for central and southern California. Meanwhile, across the eastern U.S., abnormal dryness exists across the mid-Atlantic with short-term precipitation deficits increasing across the coastal Carolinas. Although small areas of drought development may occur, designation of widespread drought development is not forecast due to uncertainty in the precipitation pattern by the second week of October. Improvement or removal is expected across most of the ongoing drought areas of Alaska. Although the onset of the rainy season is approaching, persistence is expected across Hawaii.

Tools used in the monthly U.S. Drought Outlook (MDO) included the official CPC temperature and precipitation outlooks for October 2013, various short- and medium-range forecasts and models such as the 6-10 day and 8-14 day forecasts, the NAEFS and ESRL precipitation outlooks, the soil moisture tools based on the Constructed Analog on Soil (CAS) moisture, dynamical models (CFSv2, NMME, and IMME), the 384-hour total precipitation forecasts from several runs of the GFS, the 7-day quantitative precipitation forecast from the NCEP Weather Prediction Center (WPC), climatology, and initial conditions. ENSO Neutral conditions are expected to continue through the fall.

Drought coverage and intensity remained nearly steady during September across the eastern Dakotas, Minnesota, Wisconsin, Iowa, and northern Missouri with some improvement across Illinois. Removal (D1 areas represent by the USDM) or improvement (D2 areas represented by the USDM) across the South Dakota, Minnesota, Wisconsin, and northern Iowa is based largely on expected precipitation during the first week of October. The ESRL precipitation tool for the 6-10/8-14 Day periods also indicates enhanced odds for above median precipitation. South of the predicted storm track during early October, persistence is forecast for southern Iowa, northern Missouri, and Illinois.
Forecast confidence for the Midwest is moderate.

Since the beginning of September, drought improvement occurred across western parts of Nebraska and Kansas along with the Oklahoma Panhandle, while abnormal dryness expanded across eastern Oklahoma. Additional improvement during October is not expected for most of the central and southern Great Plains since October is a relatively dry month and the CPC October outlooks calls for increased chances of below median precipitation. The exception is western Nebraska where a storm at the beginning of October could result in small areas of improvement.
Forecast confidence for the central and southern Great Plains is high but low for western Nebraska.

Drought improvement occurred during the latter half of September across central/south Texas, southwest Louisiana, and parts of Mississippi while drought intensity remained steady across northern Texas and southern Arkansas. The first week of October is expected to be dry across Texas, but a disturbance across the northern Gulf of Mexico may bring more rain and lead to drought removal across southern Louisiana. The enhanced phase of the MJO is expected to progress into the Western Hemisphere later in October. Precipitation composites associated with the expected evolution of the MJO favor improvement or removal of drought along the western/ central Gulf Coast and lower Mississippi Valley. This is consistent with the CPC October precipitation outlook calling for enhanced odds for above median precipitation across these areas.
Forecast confidence for Texas and the lower Mississippi Valley is moderate.

Due exceptionally high rainfall amounts during early-to-mid September, drought ended across northern Colorado. A very active late monsoon brought major improvements to the remainder of the Southwest. Precipitation during the first week of October is expected to be limited to the drought-free areas of northeast Colorado with mostly dry weather forecast for much of the Southwest. Therefore, persistence is likely for this region as rainfall associated with the monsoon ends.
Forecast confidence for the Southwest is high.

WPC 1-7 day precipitation forecasts indicate moderate to heavy precipitation associated with an upper-level trough across the northern Rockies. Improvement or removal of drought across parts of the northern Rockies is based primarily on this short-term precipitation although the ESRL 6-10 day precipitation on September 30 indicates a tilt in the odds towards above median precipitation for this region.
Forecast confidence for the northern Rockies is moderate.

Heavy precipitation affected the Pacific Northwest at the end of September. Climatology and precipitation tools during the beginning of October favor removal of short-term moderate drought in southwest Oregon and improvement to the severe drought in extreme northwest California. Further south, precipitation typically increases later in the fall season across the remainder of California. Therefore, persistence is forecast for central and southern California.
Forecast confidence for the West Coast is high.

The interior parts of central Alaska received near to above normal precipitation during September, while precipitation averaged below normal across a small area of southeast interior Alaska. The October drought outlook is based on trends observed in September and near to above median precipitation favored during early-to-mid October.
Forecast confidence for Alaska is moderate.

Climatology favors persistence across Hawaii although the onset of the rainy seas is approaching. Development is not forecast during the 1-month time period covered by this outlook.
Forecast confidence in Hawaii is moderate.