Latest Seasonal Assessment -
Over the past 30-days, drought persisted and/or intensified across the Northeast, the interior Southeast, Tennessee Valley, and the Lower Mississippi Valley. Surplus precipitation fell over the Atlantic Coast states from about the Delmarva Peninsula southwestward across the eastern Carolinas to northeastern Florida, resulting from the passage of former Hurricane Matthew almost two weeks ago. Surplus precipitation was also reported across the northern High Plains, the northern Rockies, the Pacific Northwest, and northern California during the past 30-days. The rainy season in the West has gotten off to a good start this year.
The seasonal drought outlook valid from October 20, 2016 to January 31, 2017 is based on various precipitation forecasts at various time scales out through 90-days, including WPC's days 1-7 precipitation forecast, CPC's Week-2, Weeks 3 and 4, and 30-day and 90-day outlooks. It is also based on dynamical climate model precipitation forecasts such as the NMME, IMME, and CFS, as well as climatology, and to a limited extent considers typical effects of a weak La Niña on the U.S. during the cold season. La Niña is favored to develop (about a 70-percent chance) during the Northern Hemisphere Fall 2016 and slightly favored to persist (about a 55-percent chance) during winter 2016-17.
Across the western contiguous U.S., there is a general model consensus regarding drought improvement and/or removal across eastern Oregon, northern portions of California, and perhaps far northwestern Nevada, with drought expected to persist farther south. In fact, drought improvement and/or removal is anticipated across most drought areas located over approximately the northern half of the Lower 48 states, which is consistent with the notion of frequent low pressure systems and accompanying upper-level troughs. This includes the northern Rockies, the northern High Plains, portions of central Pennsylvania, all but southeastern New York, and the northwestern half of New England. The one exception is over northern New Jersey, southeastern New York, and the southeastern half of New England, where dynamical model guidance does not favor strong indications for drought improvement/removal, but rather drought persistence.
The southern half of the contiguous U.S. is predicted to experience overall degradation of drought conditions, with drought persistence or intensification favored. Areas of predicted drought development include portions of the Gulf Coast region, extending across much of eastern Texas, and over parts of the southern High Plains. This latter region has recently experienced warm temperatures and gusty winds, leading to flash drought conditions on a smaller-scale. The only exception to the widespread dryness across the southern Lower 48 states includes eastern parts of both Kentucky and Tennessee, which are expected to be close enough to migratory low pressure systems passing to the north.
Elsewhere, small areas of remaining drought in both Hawaii and Puerto Rico are expected to improve and/or be removed during NDJ. The Hawaiian precipitation forecast favors above-median precipitation across the archipelago, while in Puerto Rico, the continuation of the rainy season into November favors the removal of remaining drought across both south-central Puerto Rico and the adjacent island of Vieques.
Forecast confidence for both Hawaii and Puerto Rico is moderate to high.
Forecaster: Anthony Artusa
Next Seasonal Drought Outlook issued: November 17, 2016 at 8:30 AM EDT
Seasonal Drought Outlook Discussion