Latest Seasonal Assessment -
Over the past 30-days, very dry and warm weather prevailed across much of the Nation east of the Rockies. Temperatures averaged at least 4 degF above normal across much of the lower 48 States, with anomalies of 8 to 12 degF in the northern two-thirds of the Plains. Most of the central High Plains and Southeast observed less than 25% of normal precipitation, with some locations observing no measurable rainfall. The exceptions to this were above-normal rainfall in the southern High Plains, parts of the Midwest, the eastern Great Lakes region, and portions of New England. In contrast, most of the western third of the U.S. reported surplus precipitation, except for parts of the Southwest. Not surprisingly, drought persisted or intensified across the Southeast, Tennessee Valley, lower Mississippi Valley, central Plains, and portions of the Northeast. Where surplus precipitation fell during the past 30 days, drought was improved or removed in the Northwest, a few small areas in Texas, from the central Appalachians northward into the eastern Great Lakes region, and portions of coastal new England. Drier weather in southeastern Alaska and the leeward sides of Hawaii prompted D0 development.
The seasonal drought outlook valid from November 17, 2016 to February 28, 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 6-10 and 8-14 day ERFs, Weeks 3-4, and 1- and 3-month outlooks. It is also based on dynamical climate model precipitation forecasts such as the NMME, IMME, CFS, and ECMWF, as well as statistical models, current soil moisture conditions, and climatology. It also considers typical effects of a La Niña on the U.S. during the cold season as weak La Niña conditions are present, but with only a 55% chance to persist during the winter 2016-17. The consensus expects La Niña to be short-lived, with ENSO-neutral favored beyond DJF.
Across the northern tier of the contiguous U.S., there is a general model consensus regarding a tilt toward above-median precipitation, especially in the DJF outlook. This would be expected during a La Niña event as frequent Pacific storm systems and accompanying upper-level troughs typically track across the northern third of the U.S. In the West, this expected pattern, combined with near-record October wetness in the Northwest and wet winter climatology in the Far West, should bring additional drought improvement or removal to southwestern Montana, eastern Oregon, northwestern Nevada, and northern California, although drought is forecast to persist farther south. With above-median winter precipitation also favored in the Great Lakes region and Ohio Valley, drought improvement is similarly forecast for western sections of Pennsylvania and New York where recent heavy rains have provided some drought reduction and primed the region for additional relief. Precipitation has been spottier farther east, and with no consistent guidance from the models, persistence was left in New England, eastern New York, and northern New Jersey; however, recent dryness to the south and La Niña composites and trends called for some development in the mid-Atlantic.
The southern third of the lower 48 States is predicted to tilt toward above-normal temperatures and sub-median precipitation, especially during the winter, favoring drought persistence or intensification. Combined with recent warmth and near-record dryness, areas of predicted drought development included the remaining non-drought areas of the Gulf Coast, extending westward into central Texas and the south-central Plains, and eastward into the Atlantic Piedmont. Southern and mid-Atlantic coast areas should remain drought free to the end of February due to copious rains from Hurricanes Matthew and Hermine. Drought expansion was also forecast for parts of the Southwest where the winter outlook tilts toward drier and warmer conditions, and D0 is already present. The only exception to the widespread dryness in the Southeast is improvement in the northern edge of the drought in the lower Ohio Valley (southern Indiana and northern Kentucky) where somewhat above-median winter precipitation is forecast.
Elsewhere, small areas of remaining drought in Hawaii (leeward sides of Kauai and Maui) are expected to improve or be removed by the end of February, although conditions may somewhat degrade first. The Hawaiian precipitation forecast favors above-median precipitation across the archipelago, consistent with the tendency for wet conditions when ENSO is neutral (which is expected by early 2017). In Alaska and Puerto Rico, the small remaining (non-drought) D0 areas were not expected to worsen during the winter, so no forecast was made.
Forecaster: David Miskus
Next Seasonal Drought Outlook issued: December 15, 2016 at 8:30 AM EST.
Seasonal Drought Outlook Discussion