Latest Seasonal Assessment -
A significant La Niña is currently underway, and is expected to continue throughout the Nov-Dec-Jan (NDJ) 2020-21 drought outlook period. In the West, CPC’s official 30-day and 90-day precipitation outlooks lean heavily on La Niña composites, which favor increased odds for below normal precipitation over portions of the southern and central thirds of the western CONUS. New drought development is indicated over a sizable fraction of California. La Niña also boosts the odds for increased storm activity and above normal precipitation for the northern third of the Western Region. For the High Plains Region, drought is predicted to persist, and new drought development is possible. This seems counterintuitive across the Dakotas and eastern Montana, where CPC predicts increased odds for above normal precipitation during the late autumn and early winter. However, the benefits of increased precipitation across this area are expected to be delayed, due to frozen ground which precludes soils from being adequately recharged.
In the Southern Region, dryness and drought are likely to continue, with drought expansion depicted across nearly all of Oklahoma and Texas. This is supported by the 30-day and 90-day outlooks from CPC, NDJ climatology, and La Niña composites. Dryness and drought are also expected to continue across the Midwest Region, though there is greater uncertainty regarding the outlook in Indiana and Ohio. Typically during a cold season La Niña, the Ohio Valley is favored to receive above normal precipitation which would help to alleviate any drought. However, this tilt in the odds towards above normal precipitation usually comes later in the cold season, and is less likely in NDJ. In the Southeast Region, only a few areas of abnormal dryness remain, after a very active Atlantic hurricane season (which officially ends on November 30th) and several landfalling systems along the Gulf Coast. The challenge is to determine how much drought might develop late in the NDJ season, and where. Climatology and 90-day precipitation deficits indicate one area that is more predisposed towards future drought development includes southern Georgia and northern Florida. The seasonal drought outlook for the Northeast Region is especially problematic at this time, because of the unexpectedly prolonged duration of dryness and drought in this region. La Niña composites, recent widespread ample rains (1-3”), forecast short-term heavy precipitation, and a non-dry climatology, are thought to be enough to warrant some improvement/removal of drought for most of the Northeast, with the exception of the vicinity of Pennsylvania, which has less support for any drought mitigation.
CPC’s NDJ seasonal precipitation outlook favors above normal precipitation in Hawaii, as do La Niña composites and the onset of the climatological rainy season. Therefore, drought improvement and removal is predicted across the Islands. The small area of moderate drought (D1 in the U.S. Drought Monitor) in northwest Alaska is also slated for removal, consistent with the 90-day precipitation outlook. Puerto Rico currently has no drought, thanks largely to the close passage of Tropical Storm Isaias in late July, and no development is anticipated during the early portion of its dry season (Dec-Apr).
Forecaster: Anthony Artusa
Next Seasonal Drought Outlook issued: November 19, 2020 at 8:30 AM EST.
Seasonal Drought Outlook Discussion