Tools used in the U.S. Monthly Drought Outlook (MDO) included the updated Climate Prediction Center (CPC) temperature and precipitation outlooks for October, 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), experimental weeks 3-4 outlooks, CFSv2 model forecasts, the 384-hour total precipitation forecasts from several runs of the GFS, October climatology, potential impacts from tropical storms (e.g. Matthew), and recent rainfall (since 12Z Sep. 27, the end period of the most recent U.S. Drought Monitor). 

Moderate (D1) to exceptional (D4) drought persisted and intensified over the past 4 weeks in most of the interior Southeast (northern portions of Mississippi, Alabama, and Georgia, eastern Tennessee, and western Carolinas), while abnormal dryness developed in parts of the lower Mississippi Valley (Delta) and northward into the mid-Atlantic. In contrast, moderate to heavy rains from Hurricane Hermine and Tropical Storm Julia helped remove drought (D1) across the eastern Gulf, southern, and mid-Atlantic Coasts. Unfortunately, the forecasts at all time-scales (QPF, ERFs, Weeks 3-4, updated October precipitation, and even the 3-month [OND] precipitation) favor sub-median rainfall for the interior Southeast. Even the climatology for October shows a drier time of year with many areas normally receiving only 3.5-5% of their annual total (an evenly-distributed monthly climatology would get between 8-8.5% of its annual amount). In the interior Southeast where the past 30 days were extremely dry and warm, drought persistence is an obvious choice while drought development where D0 already exists is likely by the end of October. The only factor that may impact this forecast is Hurricane Matthew, currently in the south-central Caribbean. The current model consensus is to take Matthew northward up the Atlantic Coast, but a few model runs have Matthew moving farther west and entering the Gulf of Mexico, with possible landfall in the Southeast. Although this scenario appears to be unlikely, there is enough concern to lower the confidence in the eastern sections of the Southeast. Farther north, however, a stalled upper-air low has produced moderate to heavy rains in most of the mid-Atlantic during the past few days, thus halting the potential northward spread of drought and likely eliminating the recently-added D0.

Forecast confidence is moderate (eastern areas) to high (western sections) for the interior Southeast. 

With the past 30-days experiencing above-average temperatures (2 to 5 degrees F above normal) and subnormal rainfall (deficits of 1 to 4 inches), dryness and drought intensified across parts of the Northeast, including a recent new large area of D0 southward into the mid-Atlantic and a 2-category downgrade in southern Maine. As mentioned in the Southeast narrative, a slow-moving upper-air low has drenched most of the mid-Atlantic the past few days, with additional rains expected in portions of southern and coastal New England westward into the eastern Great Lakes region. The already-fallen and forecasted rains should be enough to not only prevent further deterioration to D1 in the mid-Atlantic, but also to remove the recently-added D0 area. In addition, moderate rains from the upper-air low in eastern lower Michigan, northeastern Ohio, northern Pennsylvania, and New Jersey should be enough for a 1-category improvement, while more light to moderate precipitation is forecasted for these areas during the next 3 days. In coastal New England, although the recent heavy rains have yet to reach this far north, 2-3 inches are forecast in the next few days, possibly providing some improvement here. Plus, the fall is an ideal time for soil moisture recharge as temperatures drop, evapotranspiration is minimal, and the ground is unfrozen. The latest guidance for the track of Hurricane Matthew now turns the storm away from the coast and out to sea, so no rain is expected from Matthew in New England during early October. In contrast, decent rains are forecast to stay south of northern and western sections of New England where 7-, 14-, and 28-day average USGS stream flows are at well below-normal levels for this date, thus persistence is favored here.

Forecast confidence for the Northeast is: moderate for western and northern areas (persistence); moderate to high in southern sections (improvement), and low to moderate (improvement) for coastal New England. 

Since late August, above-normal rains fell on the western half of Texas and eastern New Mexico northeastward into the upper Midwest, resulting in drought improvement in the Texas Panhandle, most of New Mexico, and west-central Oklahoma. Unfortunately the rains bypassed eastern Oklahoma and areas to the east (lower Mississippi Valley and interior Southeast), maintaining, and in some areas, intensifying and expanding dryness and drought. As a result, a few small D1 areas were left in eastern New Mexico, the Texas Panhandle, extreme southern Texas, and eastern Oklahoma (with some D2). The forecast for the southern Plains features a mixed (but tilting more dry) signal for October (QPF [Days 1-7] dry, ERFs: 6-10 day favors above-median precipitation, 8-14 day tilted toward dry, good odds for sub-median rainfall in eastern areas in the experimental weeks 3-4 and updated October outlook while the recent 15-year trend October climatology was somewhat wet in Texas. Although the overall signal is tilted more toward dryness during October, the recent wet pattern in western sections at 30- and 60-days suggests leaving conditions as is, although the odds for development are more possible in eastern portions where D0 exists and where it was been dry during the past 30-days. 

Forecast confidence for the southern Plains is moderate.

Near- to above-average rainfall and slightly above-normal temperatures were observed across most of the northern and central Plains during the past 30- and 60-days, although a few areas (central Nebraska, northern Colorado) were much drier during both periods. Given these short-term conditions and recent drought improvements, along with favorable chances of above-median precipitation in the extended range (days 6-10 and 8-14) and the updated October precipitation outlook, northeastern Wyoming, southeastern Montana, western South Dakota, south-central Nebraska, and northern Colorado are primed for drought improvement, especially with the added benefits of reduced temperatures and minimal evapotranspiration.  

Forecast confidence for the north-central Plains is moderate.

Similar to the north-central Plains, a deep trough of low pressure is expected to be in place over the northern Rockies and Plains during most of October which should produce unsettled weather. This is featured in most of the monthly forecasts, including light to moderate precipitation in the QPF and good odds for above-median precipitation in the 6-10 day ERF, experimental weeks 3-4 outlook, and the updated October precipitation outlook.  However, because of the protracted nature of the drought in parts of the northern Rockies, this precipitation may not be enough for any improvement by Oct. 31, although overall, more improvement than persistence should be seen in northwestern and southwestern Montana, eastern Idaho, and northwestern Wyoming. 

Forecast confidence for the northern Rockies is moderate.

Drought persistence is expected across the ongoing drought areas of California and the western Great Basin as October is still a dry time of year. Farther north, however, precipitation typically begins to increase as October normally marks the start of the Pacific Northwest rainy season. In addition, with the QPF forecasting 1.5-3 inches of rain along the northern California, Oregon, and Washington coasts, both the ERFs, and the experimental weeks 3-4 and updated October precipitation outlooks favoring above-median rainfall, removal of the D1 along coastal Oregon and Washington is likely by Oct. 31. In eastern Oregon, although the odds favor above-median precipitation in the extended range forecasts, its climatology amounts are still relatively small, thus less likely that enough rain would occur to eliminate the drought by the end of the month.

Forecast confidence for the Pacific Northwest Coast and eastern Oregon is moderate to high; California and Great Basin is high.

With the Southwest monsoon normally approaching its end during during late September into October, rainfall dramatically falls off until later in the winter season when a second peak typically occurs. Although light to moderate (0.5-1 inch) rains are forecast for the next 7-days in eastern Arizona and western New Mexico, the extended range forecasts tilt toward sub-median precipitation, while the updated October precipitation outlook has no odds (EC). With no obvious drought-ending rains on the horizon, persistence is forecast for the Southwest and eastward into the Texas Panhandle. The remote possibility of receiving tropical moisture from an east Pacific tropical system (such as Newton in early September) slightly lowers the confidence in this forecast for October. 

Forecast confidence for the Southwest is moderate.

During the past El Nino, drought coverage peaked at nearly 80 percent of the Hawaiian Islands in early April, but since then increased and widespread rainfall, some attributed to moisture from tropical systems, has reduced drought coverage to about 1 percent. This included small D1-D2 areas on the leeward sides of Kauai and Maui. With recent wetness this summer and a good probability of above-median rainfall during October, drought improvement is expected for the lingering small drought areas on western parts of Kauai and Maui.

Forecast confidence for Hawaii is high.

A small area of moderate drought (less than 5 percent coverage) has persisted across south-central Puerto Rico since mid-2015. Based on a relatively wet climatology and the decent potential for tropical systems to affect Puerto Rico, removal is forecast. The one factor decreasing the confidence is the length of the drought (almost 17 months) and the long-term deficit (more than 16 inches).

Forecast confidence for Puerto Rico is moderate to high.

Forecaster: David Miskus

Next Monthly Drought Outlook issued: October 31, 2016 at 3pm PM EDT