U.S. Monthly Drought Outlook

30 Nov U.S. Monthly Drought Outlook

Published by the National Weather Service
Climate Prediction Center
Released November 30, 2013

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Latest Monthly Assessment – The December 2013 Drought Outlook is based on initial conditions, short and medium range forecasts, the CPC updated monthly outlooks for temperature and precipitation, and climatology. During the first half of November, relatively tranquil conditions prevailed across the lower 48 States, with light to moderate precipitation limited to the Pacific Northwest Coast, and from extreme southern Texas northeastward into the upper Great Lakes region. Very dry weather continued in the Southeast and New England as 90-day precipitation was less than half of normal, accumulating deficits between 4 and 8 inches. In addition, the wet season has been slow to commence in northern California and southern Oregon, with even lower precipitation percentages (<25%) and larger deficits (up to 12 inches) since October 1. With the first half of December expected to be drier than usual and the central West Coast station normals rather high, some development was added where D0 existed.

After mid-month, weather conditions finally changed as a vigorous upper-level storm dropped plentiful moisture on the Southwest and slowly tracked eastward, tapping Gulf moisture. With the precipitation from the late November storm already improving drought conditions in Arizona plus favorable odds of above-median precipitation in the Four Corners region in early December – versus a contradictory tilt of below-median precipitation for DJF, no changes were made for December in the Southwest. Farther north, however, with the recent precipitation, 1- and 3-month probabilities of above-median precipitation, and short-term odds for wetness, improvement and removal was made in Idaho, Utah, and Wyoming, and extreme northern Arizona and New Mexico. Farther east, widespread and ample precipitation fell on the southern Plains, lower Mississippi Valley, most of the Southeast, and the Atlantic Coast States during the last week of November, putting a significant dent in the month-to-date (MTD) deficits, or in some areas, creating MTD surpluses. But with short-term, 1-, and 3-month forecasts pointing toward sub-median precipitation in the southern High Plains, some development where D0 existed was added to western Texas and southern New Mexico. In eastern Texas and central Arkansas, recent wetness, surpluses out to 90-days, and short-term forecasts for above-median rain should be enough to remove lingering D1 areas.

Some drought development is possible across parts of the Southeast, especially in Florida where D0 already exists, short-term and monthly forecasts edge toward dryness, and 28-day USGS stream flows are low. Development is a bit more uncertain in Alabama and Georgia as short-term forecasts hint at above-median rainfall, the monthly precipitation is EC (equal-chances), and the seasonal precipitation outlook tilts toward dryness. Therefore, development was added in the areas with the greatest 90-day deficits, where recent rainfall was less, and stream flows were below normal. Short-term drought also expanded across coastal New England in mid-November, but with recent heavy rains reducing 90-day deficits and early December forecasts pointing toward wetness, removal of D1 is anticipated before the ground freezes. December is a climatologically dry time of year across the upper Midwest and Plains. With no clear signal during early December and slight odds for below-median December precipitation from the southern Plains northeastward into Missouri, drought persistence is most probable in these regions.

In Alaska, wet and mild weather has continued in east-central Alaska, edging year-to-date percentages closer to normal and improving the chances for drought reduction. In Hawaii, a wet first half of November was replaced by much drier weather during the second half, but both the monthly and seasonal precipitation outlooks call for above-median rainfall, hence the improvement.

Forecaster: D. Miskus

Next Monthly Drought Outlook issued: December 31, 2013 at 3:00 PM EDT