Tools used in the monthly U.S. Drought Outlook (MDO) included the official CPC temperature and precipitation outlooks for
September 2013, various short- and medium-range forecasts
and models such as the 6-10 day and 8-14 day forecasts, the NAEFS 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.
A late summer flash drought occurred recently across parts of the Midwest where 30-day rainfall deficits are 2 to 5 inches across southern
Indiana, Illinois, Iowa, northern Missouri, Minnesota, and southern Wisconsin. Following below normal temperatures during early to
mid-August, maximum temperatures in the 90s during the final week of August intensified drought conditions, stressing corn and soybeans,
and degraded pasture conditions. As of August 29, Champaign and Decatur, Illinois have recorded less than 0.1 inches of rainfall during
August. Many locations across the Midwest are expected to have one of their driest Augusts on record. On August 28 and 29, moderate to
locally heavy rain mostly fell to the north of these new drought areas. Since the first half of September is expected to remain relatively
dry, persistence and additional development are forecast for the Midwest. Short-term drought expansion farther east across the Ohio Valley
is possible, but the 1-3 Day WPC precipitation outlook indicates moderate rainfall and the CPC monthly outlook indicates enhanced odds for
above median precipitation across most of Indiana and Ohio.
Forecast confidence for the Midwest is high.
Similar to the Midwest flash drought, the eastern Dakotas have experienced a rapid development of drought during the past month. Since no
precipitation tools offer a wet signal during September, persistence is forecast for the eastern Dakotas.
Forecast confidence is high for the eastern Dakotas.
Tropical Storm Ivo tracked near the Baja California Peninsula from August 23-25 and resulted in a surge of low-level moisture north from
the Gulf of California to the desert Southwest. Heavy rain triggered flash flooding across western Arizona and southern Nevada. Tropical
Storm Juliette developed on August 28 and also tracked north near the Baja California Peninsula, contributing to a persistence of deep
monsoon moisture across the Southwest. Locally heavy rain is expected to continue into the beginning of September across Arizona,
southwest Colorado, western New Mexico, and southern Utah. The 6-10/8-14 Day outlooks favor above median precipitation across these areas.
Although the monsoon begins to wane during September, improvement or drought removal (moderate/D1 areas currently designated in the U.S.
Drought Monitor), is forecast for the Southwest.
Forecast confidence is high for drought improvement or removal across Arizona, southwest Colorado, western/northern New Mexico, and
Although the 6-10/8-14 Day precipitation outlooks tilt the odds towards above median precipitation, persistence is expected for the
long-term drought areas of the Great Basin and northern half of the northern Rockies through the end of September. Unseasonably warm
temperatures during late August and early September could intensify drought conditions across parts of this region
Forecast confidence is moderate for the Great Basin and northern half of the Rockies.
A sharp gradient in drought conditions exists across the central and southern Great Plains. According to the U.S. Drought Monitor on August
27, extreme (D3) to exceptional (D4) drought exists across the central and southern high Plains with eastern Kansas and northeast Oklahoma
drought-free. Precipitation tools for early September, including the WPC 1-5 day precipitation forecast and CPC’s 6-10 Day precipitation
outlooks favor below median precipitation across the central and southern Great Plains. Therefore, persistence is expected for the central
and southern Great Plains. However, forecast confidence decreases across the central and southern high Plains where the 384-hour total
precipitation forecasts from several past runs of the GFS indicate the potential for moderate to heavy rainfall across this region.
Forecast confidence is moderate for the central and southern Great Plains.
Climatology supports improvement across south Texas, but precipitation tools including the NAEFS indicate a dry signal during early
September. Since the CPC monthly outlook calls for equal chances of below, near, or above median precipitation for south Texas, the
expected dry start to September favors persistence.
Forecast confidence is low for south Texas.
Persistence is forecast for ongoing drought areas of the lower Mississippi Valley where the 6-10/8-14 Day Outlooks favor dryness and the
CFSv2 indicates near to below median precipitation in this region. In addition, September is a relatively dry time of year for southern
Arkansas and northern Louisiana.
Forecast confidence is high for the lower Mississippi Valley.
The wet season typically begins later in the fall season along the West Coast with September remaining a relatively dry time of year.
Climatology favors persistence along the West Coast.
Forecast confidence is high for the West Coast.
Removal of the southwest part of the ongoing drought area across Alaska is based on seasonably cooler temperatures and increased chances
for above median precipitation during the first half of September. For the remainder of the Alaska drought area, forecasted lighter
precipitation amounts favor persistence.
Climatology favors persistence across Hawaii. Development is not forecast during the 1-month time period covered by this outlook.
Forecast confidence in Hawaii is moderate.