Latest Seasonal Assessment - During the past three weeks (since May 16), an active weather pattern, consisting of a series of slow-moving storm systems tracking across the northern tier of the Nation, brought ample rainfall to the Pacific Northwest, the northern thirds of the Rockies and High Plains, much of the Great Plains, Midwest, Delta, Great Lakes Region, New England, and southern half of Florida. 3-week temperatures have averaged below normal in the Northwest , northern Rockies and Plains, and upper Midwest. Since May 1, the heaviest rains (more than 7 inches) have fallen on parts of the northern High Plains, the middle Mississippi Valley, central Great Plains, the upper and lower Delta, parts of Florida, and the southern Appalachians. In contrast, drier conditions were observed in the Southwest, the southern Rockies and High Plains, portions of the Southeast, especially Alabama, the eastern Ohio Valley, and the mid-Atlantic.

Meanwhile, ENSO-neutral conditions persisted across the tropical Atlantic, with most models forecasting no major changes to conditions into Fall 2013. In addition, the 2013 Caribbean and Atlantic hurricane outlook (released May 23) called for an active, above-normal season. There was a 70 percent likelihood of 13-20 named storms, of which 7-11 could become hurricanes, including 3-6 major hurricanes. The normal season averages 12 named storms, 6 hurricanes, and 3 major hurricanes. This does not imply, however, that the storms will make landfall, but an active tropical season would increase odds that some of the storms will impact land.

Year-to-date (YTD) precipitation (to June 4) has been subnormal in much of the West, southern Plains, central High Plains, parts of Florida, eastern North Carolina, and most of the northeastern quarter of the Nation. Coincidentally, the precipitation pattern since April 1 is similar to the YTD percentages, except for wetter conditions in the Northwest , Texas, northern New England, and Florida. The greatest YTD deficits (more than 8 inches) were limited to the Far West along the Washington, Oregon, and California coasts, and in the Cascade and Sierra Nevada Mountains. Deficiencies since January 1 exceeding 4 inches were found from the eastern Ohio Valley into coastal New England, coastal North Carolina, west-central Florida, and parts of Texas, western Oklahoma, and southwestern Kansas. In contrast, surplus precipitation has fallen on the northern thirds of the Rockies and Plains and upper Midwest southward to the central Gulf Coast, in most of the Southeast, and the southern Appalachians. In a sharp contrast to last year at this time, YTD temperatures have averaged below normal across most of the lower 48 States, especially in the northern Plains and upper Midwest (-4 to -8 degF), with slightly above normal readings limited to New England, California, and parts of Texas and Florida.

Accordingly, drought expansion occurred over the past 3 weeks in the West and Southwest. Abnormal dryness and drought briefly expanded in parts of the Northwest and Northeast 2 weeks ago, but recent rains have pared back much of the increase. In contrast, improvements were made along the northeastern and eastern edges of the main drought area in the Nation’s midsection, in the Southeast, and parts of the Northeast. The worst conditions (D3 to D4) have stubbornly persisted in the southern and central High Plains, although this area just recently received welcome rains (1-3 inches).

The updated June temperature and precipitation outlooks (released May 31) favored below median rainfall in the Northwest and southern and central High Plains, above median precipitation odds in the eastern Gulf and southern Atlantic Coasts and southeastern Alaska, and equal chances elsewhere. A tilt toward above-median June temperatures were forecast for most of the western third of the U.S., with the best chances for above median readings in the Great Basin and Oregon. Some of the dynamical models hinted at cool and wet June in the eastern half of the Nation, but they were not consistent and skillful enough to be included in the monthly outlooks.

The seasonal temperature and precipitation outlooks (released May 16 with no update) are somewhat similar to the updated monthly outlooks, with odds for below median rainfall in the Northwest and southern and central High Plains. A small area of above median rainfall was drawn along the central Gulf Coast and in southeastern Alaska. Above median temperatures are also favored for most of the West, with the highest odds in the southern halves of the Rockies and High Plains. In addition, the chances for above median warmth extended eastward along the Atlantic Coast, with slightly higher probabilities centered over the Northeast. For the southwestern summer monsoon, a slight tilt toward below median rains was indicated in eastern areas (e.g. New Mexico and west Texas).

Although CPC odds favored subnormal June and JJA rainfall, spring rains continued into late May across most of Hawaii, eliminating drought on Kauai, Oahu, and most of Molokai. But with the normal wet season tapering off and the southern islands observing subnormal March and April rains, persistence remained on the leeward sides of Maui and the Big Island, with development possible on their windward sides. In Alaska, the Koyukuk Basin of north-central Alaska was left as some improvement with no tilt in odds either way (e.g. equal chances) for June and JJA precipitation.

Forecaster: D. Miskus

Next Outlook issued: June 20, 2013 at 8:30 AM EDT

Seasonal Drought Outlook Discussion