Tools used in the U.S. Monthly Drought Outlook (MDO) included the updated Climate Prediction Center (CPC) temperature and precipitation outlooks for September, various short- and medium-range forecasts and models such as the 7-day quantitative precipitation forecast (QPF) totals from the Weather Prediction Center (WPC), the 6-10 day and 8-14 day CPC extended-range forecasts (ERFs), CFSv2 model forecasts, the 384-hour total precipitation forecasts from several runs of the GFS, climatology for September, and recent rainfall. 

Moderate (D1) to extreme (D3) drought persisted across parts of Alabama, Georgia, and the southern Appalachians while drought coverage decreased across Mississippi since late July. Soil moisture ranks in the lowest 10th percentile across northwest Georgia. Heavy rain associated with Tropical Storm Hermine emerging from the Gulf of Mexico is likely to eliminate moderate drought from coastal Georgia and South Carolina, and also end abnormal dryness in other parts of southeast Georgia and northeast Florida. Due to a westward shift with the track of this tropical system in the latest model guidance, drought removal is forecast for the southern and eastern extent of the ongoing drought across Georgia and South Carolina. The CPC updated monthly outlook indicates enhanced odds of below-median precipitation across the Tennessee Valley. The CFSv2 monthly outlook has a consistent dry signal across the interior Southeast. Considering these factors, persistence is forecast for the remainder of the drought area across the Southeast, with development most likely across northeast Alabama and eastern Tennessee. Forecast confidence is low due to continued uncertainty on the track of Tropical Storm Hermine and any future tropical cyclones that could emerge from the Atlantic or Gulf of Mexico during September.

Forecast confidence is high for coastal Georgia and South Carolina but low for the remainder of the Southeast. 

Above-average temperatures (1 to 4 degrees F above normal) and a continued lack of adequate rainfall (deficits of 1 to 3 inches) resulted in drought intensification across parts of the Northeast during August. According to the U.S. Drought Monitor, extreme drought (D3) is currently designated for parts of western New York, southern New Hampshire, and eastern Massachusetts. Low streamflows remain one of the major impacts associated with the worsening drought conditions. The U.S. Geological Survey indicates that 28-day average streamflows are in the lowest 10th percentile or at record low levels in these D3 areas. The future evolution of Tropical Storm Hermine, emerging from the Gulf of Mexico, becomes even more uncertain with time, but it could eventually bring heavy rain to at least part of the drought-affect region of the Northeast. Recent model guidance continues to shift heavier rainfall westward to include part of the Northeast. The improvement or removal of drought in Long Island and southeast New England is consistent with these latest model trends and the updated CPC monthly precipitation outlook. Elsewhere, across the Northeast, persistence is most likely due to longer-term drought conditions and persistent upper-level ridging. 

Forecast confidence is moderate for most of the Northeast but low for Long Island and southeast New England. 

Short-term drought coverage generally decreased across lower Michigan and northern Ohio since late July. Due to recent rainfall, removal is likely for the lingering drought areas of lower Michigan, northeast Indiana, and northwest Ohio. Persistence is forecast across northeast Ohio where 60 to 90-day precipitation deficits are larger according to the Advanced Hydrological Prediction Service (AHPS). Also, this area is expected to be relatively dry during early September. 

Forecast confidence is moderate for northeast Indiana, Ohio, and lower Michigan.

During the past 30 days, an axis of above-normal rainfall has extended from the Big Bend of Texas and southeast New Mexico northeast to the lower Missouri River. Drought removal is likely across southeast New Mexico and west Texas due to recent heavy rainfall and predicted rainfall during the next few days. Farther to the north, drought removal is also forecast for northwest Kansas, southern Nebraska, southern Iowa, and northern Missouri due to recent wetness. Lingering drought across southern Texas also is primed for removal during the next month. The extended range forecasts indicate a tilt in the odds for above-median rainfall across much of Oklahoma. Therefore, removal is forecast for the small drought areas that exist across central and eastern Oklahoma.

Forecast confidence is high for eastern New Mexico and west Texas and moderate for the remainder of the central and southern Great Plains.

Near- to above-average rainfall was observed across the northern Great Plains during the past 30 days. Given these initial conditions, parts of South Dakota and adjacent areas of Nebraska are primed for drought removal or improvement. Also, the CPC updated monthly outlook indicates enhanced odds for above-median precipitation across the eastern half of South Dakota. Persistence is forecast for areas of the northern Great Plains where soil moisture ranks in the lowest 30th percentile. Otherwise, drought improvement or removal is forecast for the remainder of the drought areas across the northern Great Plains. 

Forecast confidence for the northern Great Plains is low.

Drought persistence is forecast across the long-term drought areas of the northern Rockies due to the protracted nature of the drought. Also, precipitation signals from the tools are mixed. Development forecast for eastern Idaho and northwest Wyoming, is based on 30-day precipitation deficits and very low 28-day streamflows. 

Forecast confidence for the northern Rockies is moderate.

Drought persistence is expected across the ongoing drought areas of the Pacific Northwest due to a relatively dry climatology and the CPC updated monthly outlook favoring below-median precipitation. Development is likely across Oregon where soil moisture ranks in the lowest 20th percentile and is south of any predicted rainfall during the next week. Farther to the south, a dry climatology during September favors persistence across California and the Great Basin.

Forecast confidence for the Pacific Northwest, California, and Great Basin is high.

Rainfall expected during the next week along with a relatively wet climatology through September favors improvement or removal of drought across southeast Arizona and western New Mexico. However, forecast confidence is low considering that monsoon rainfall in these areas is typically convective and scattered. Persistence is forecast for the remainder of Arizona, although forecast confidence is reduced since past model runs have indicated a surge of tropical moisture north from the east Pacific. 

Forecast confidence for Arizona and western New Mexico is low.

During the past El Nino, drought coverage peaked at nearly 80 percent of the Hawaiian Islands in early April. Since that time, that coverage decreased and is currently less than 15 percent. As of August 31, a pair of tropical cyclones (Hurricane Madeline and Lester) are forecast to bring enhanced rainfall to the Hawaiian Islands at the beginning of September. Therefore, drought removal is expected for the lingering drought areas across Hawaii.

Forecast confidence for Hawaii is high.

Only a small area of moderate drought (less than 7 percent coverage) persists across Puerto Rico. Based on a relatively wet climatology and the potential for tropical systems to affect Puerto Rico, removal is forecast.

Forecast confidence for Puerto Rico is high.

Forecaster: Brad Pugh

Next Monthly Drought Outlook issued: September 30, 2016 at 3pm PM EDT