Rapid onset and intensification of drought occurred across the Southeast, mid-Atlantic, and Ohio to Tennessee Valleys since late August. This “flash drought” was a result of sparse rainfall coupled with periods of abnormal heat during September.
Much needed rainfall was ongoing across the eastern U.S. on October 16 as a coastal low pressure system developed. Additional beneficial rainfall is forecast during the next week which may be enhanced by a tropical system tracking northeast from the Gulf of Mexico. Heavy rainfall during mid-October is likely to ameliorate drought conditions from the Florida Panhandle northeast to the mid-Atlantic.
This short-term relief and a favorable time of year for soil moisture recharge throughout the outlook period support drought improvement and removal along and east of the Mississippi River. Improvement and removal are also expected across eastern Texas by the end of January 2020, based largely on climatology and a favorable time of year for soil moisture recharge.
Persistence is more likely farther to the west across the southern Great Plains and Southwest where the climatology is drier during the outlook period. The most likely area for development exists across northern and central California based on below normal precipitation during October and enhanced odds that below normal precipitation persists from November 2019 through January 2020.
A wet climatology favors improvement or removal across Alaska and Hawaii, while persistence is forecast for drought across southern Puerto Rico.
Forecast confidence is high for the Southeast Region.
- Insufficient rainfall coupled with record heat resulted in rapid development and intensification of drought across the Southeast.
- As of October 15, 60-day precipitation deficits exceed 4 inches from Virginia southwest to the southern Appalachians and Florida Panhandle. Soil moisture ranks in the lowest one percentile across many of these areas.
- Despite these dry initial conditions, a number of factors favor improving drought conditions or even removal of drought during the outlook period. These factors include the ongoing widespread rainfall, likelihood of additional rainfall (1 to 2 inches, locally more) during the next week, and the short-term nature of the drought.
- As of October 16, the National Hurricane Center states that there is a 50 percent chance that a tropical or subtropical cyclone develops over the Gulf of Mexico. Regardless of development, heavy rainfall is forecast to spread inland across the Southeast on October 19 and 20.
- The next three months is a favorable time of year for soil moisture recharge as evapotranspiration rates decrease. Based on these factors, removal is forecast for short-term moderate (D1) and severe (D2) drought areas on the U.S. Drought Monitor, valid on October 15.
- Improvement is forecast for the D3 (extreme) drought areas. Drought amelioration is likely to occur across much of the ongoing drought areas from the Florida Panhandle northeast to the mid-Atlantic during the next week.
Forecast confidence is moderate for the lower Mississippi Valley and low for Texas of the Southern Region.
- The flash drought also has affected parts of the lower Mississippi Valley and Texas during the past month.
- Excluding the torrential rainfall associated with Tropical Storm Imelda, 30-day precipitation deficits range from 2 to 4 inches from the lower Mississippi Valley west to the Hill Country of Texas.
- Based on recent rainfall (locally more than 2 inches) and a favorable time of year for soil moisture recharge, improvement or removal of drought are forecast for the lower Mississippi Valley.
- Forecast confidence decreases farther to the west across Texas. Although little or no drought relief is expected through the end of October, a wetter climatology favors improving drought conditions by the end of January across eastern Texas. Persistence is more likely across western Texas due to a drier winter climatology.
Forecast confidence is high for the Midwest Region.
- The rapid onset of drought has also expanded north to affect the Ohio Valley.
- Although the heaviest rainfall is likely to occur southeast of the Ohio River during the next week, short-term drought is unlikely to persist through the end of January.
- Mid-latitude low pressure systems during the next three months can result in widespread precipitation across the ongoing drought areas.
- Given the absence of dry signals among seasonal precipitation tools and a favorable time of year for soil moisture recharge, drought removal is likely by the end of January.
Forecast confidence is high for the High Plains Region.
- The Missouri River Basin remains excessively wet with many areas receiving 200 to 400 percent of normal precipitation during the past 90 days. Soil moisture ranks in the 99th percentile from North Dakota south to Nebraska. Therefore, drought development is unlikely for the northern and central Great Plains.
- A small area of moderate drought is ongoing across southwest Kansas. Although the seasonal outlook favors above normal precipitaton across this region, persistence is forecast given the relatively dry time of year across the High Plains.
Forecast confidence is low for the West.
- A lack of summer monsoon rainfall resulted in drought development across the Four Corners region since July. 90-day precipitation deficits exceed 4 inches in parts of Arizona, southwest Colorado, western New Mexico, and Utah.
- Precipitation through the end of January is unlikely to alleviate drought throughout much of the Four Corners region. However, chances of improvement/removal are higher across the Colorado Rockies where a wetter signal exists on the seasonal time scale.
- An amplifying upper-level ridge along the West Coast is likely to maintain a dry pattern across California through the end of October.
- Development is forecast for parts of northern and central California due to below-normal precipitation during October along with the monthly and seasonal outlooks favoring below normal precipitation.
Forecast confidence is high for the Northeast Region.
- After the Northeast region remained drought-free dating back to early November 2018, a recent period of below normal precipitation and above normal temperatures resulted in an expansion of moderate drought (D1) north into parts of Delaware, Maryland, and southeast Pennsylvania.
- Ongoing heavy rainfall, the absence of a dry signal among seasonal precipitation tools, and a favorable time of year for soil moisture recharge support removal of short-term moderate to severe drought.
- Many areas are likely to experience drought relief during the next week.
Forecast confidence is high for Alaska.
- Drought improved by one to two categories across the southern mainland of Alaska, including the Kenai Peninsula. Drought removal is likely for any lingering drought across these areas based on increased chances for above normal precipitation at all time scales.
- Removal or improvement for the Alaska Panhandle is consistent with a wet climatology and the seasonal precipitation outlook. Although long-term drought impacts, such as hydro power, continue for parts of the Alaska Panhandle, the recent increase in precipitation has raised lake levels.
Forecast confidence is high for Hawaii.
- Drought improvement continues across Hawaii with coverage decreasing from 21.67 percent in late August to 14.10 percent in early October.
- Based on a wetter climatology during December and January along with the seasonal precipitation outlook, continued improvement and removal of drought are likely by the end of January.
Forecast confidence is low for Puerto Rico.
- Moderate drought is limited to southern Puerto Rico with less than 10 percent of the island designated with drought. Since the climatology becomes increasingly dry during the outlook period, peristence is forecast.