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Climate Prediction Center


September-November 2005


Latest Seasonal Assessment - The latest seasonal drought outlook indicates that some additional improvement is likely over the drought area extending from the western Great Lakes southward into northern Missouri. There is considerable uncertainty about the timing and extent of any improvement in the region, as the seasonal precipitation outlook for September-November indicates equal chances for wet or dry. Farther south, the odds are higher for improvement from central Missouri into Arkansas and northeast Texas. The odds also favor improving drought conditions in southern Texas, which is poised to enter its wettest time of the year. In the Ohio Valley and the East, despite some sporadic rains, August has seen worsening dryness in Kentucky and parts of Ohio, western Pennsylvania, and western New York. Although some rain is in the short-term forecasts, the drought areas are expected to largely persist into autumn, with a good chance that drought may expand into additional areas of Ohio, Pennsylvania, and West Virginia. In the plains, improving drought conditions are likely in central and eastern Nebraska, with more limited relief from western Nebraska into eastern Wyoming. Drought should persist in the northern Rockies and Pacific Northwest, and there is a possibility that drought could expand across southern Oregon and into northern California and northwestern Nevada. The odds favor below-normal precipitation during September-November from Montana into Idaho, Oregon, Nevada and northern California. In the Southwest, seasonal monsoon rains should continue to provide short-term relief for lingering long-term drought areas in Arizona and New Mexico, with the greatest odds for improvement in southwest New Mexico and southeast Arizona.

Discussion for the Seasonal Drought Outlook

Tools used in the Drought Outlook included the official CPC long-lead precipitation outlook for September-November, the drought termination and amelioration probabilities for November, various medium and short-range forecasts and models such as the 6-10 day and 8-14 day forecasts, and the soil moisture tools based on the GFS model and the Constructed Analogues for the season.

This month's outlook depicts limited improvement for the drought area extending from Michigan and Wisconsin southward into northeastern Missouri. With the official CPC seasonal outlook for September-November indicating equal chances for wet or dry and warm and cool, there is much uncertainty in this part of the country. Various medium-range model runs from August 16 and 17 suggest parts of this region should see heavy rains during the first 2 weeks of the outlook period, and the official 5-day forecast calls for more than 1 inch of rain across Wisconsin and northern Illinois, so there is support in the short term for continuing last month's forecast of improvement across the Great Lakes into northern Illinois. But some long-range forecast tools imply a slight tilt toward below-normal rainfall for the region, with the new consolidated model depicting below-normal rainfall for Wisconsin and northern Illinois during September-November. Similarly, the Palmer drought probability data for November indicates difficulty in achieving drought improvement for this time of the year from Illinois northward. As a result, a depiction of limited improvement seemed like the best bet at this time. Farther south, the seasonal odds show a better chance for drought improvement from Missouri southward into Texas, based on the historical data. Also, the consolidated model depicts a tilt toward wetness over eastern Texas for September-November. September is the wettest month of the year in South Texas, so this forecast period could show significant relief for those areas that did not see enough relief from Hurricane Emily in July.

In the East, severe drought has recently developed along the Kentucky-Ohio border, and drought extends from western Pennsylvania into parts of upstate New York. The 2-week forecast from the CPC soil moisture model shows increasing deficits in this region, and the consolidated precipitation model for September-November depicts a tilt toward dryness in eastern Kentucky and most of Ohio. The CAS soil model depicts significant deficits persisting from northern Kentucky into western New York through at least November. The drought outlook calls for persisting drought for the region, with a good chance that the drought area in Ohio-Kentucky will connect with the Pennsylvania-New York area. The outlook is more confident that the drought will continue in the Ohio area than in the New York area, as the latter area could be more susceptible to tropical storm remnants.

With the official seasonal outlook depicting below-normal precipitation for the Northwest, the drought outlook shows persisting drought in this region, with a transition toward more improvement eastward from eastern Wyoming into Nebraska based on medium and long-range forecasts. The area of expansion into northern California is based on the seasonal outlook for precipitation and the current low soil moisture shown by the University of Washington's soil model. The Southwest should see a strong influx of moisture from Mexico in the next 2 weeks, resulting in additional short-term improvement for the lingering long-term drought areas in this region. The transition from D1 to D0 is most likely in the area that extends to the Mexican border.

NOAA/ National Weather Service
NOAA Center for Weather and Climate Prediction
Climate Prediction Center
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Page Author: Climate Prediction Center Internet Team
Page last modified: December 13, 2006
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