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Climate Prediction Center


September - November 2003


Latest Seasonal Assessment - Hot, dry weather intensified drought across much of the Great Plains during the first 3 weeks of August, with the Kansas-Missouri area recording triple digit heat from August 16-20, and scattered locations from Texas to Minnesota reporting negligible rainfall for the month to date. Some of the dryness has been very persistent. As of August 20, there had been no measurable rain in Lubbock, Texas since June 26. The seasonal outlook through November calls for drought to essentially persist from the Dakotas into Kansas and Missouri, although cooler weather and scattered bouts of rain will bring occasional relief to the region. The odds for relief are better in the southern Plains, as the outlook calls for improvement from southern Kansas into Texas. However, the confidence in the drought outlook is low for the Plains states, as there are no strong indications of above or below normal rainfall during September-November. In the West, summer thunderstorms have brought scattered relief as expected, and even flooding, but high temperatures have offset some of the rain's beneficial impacts. Continued scattered improvement is expected from the Southwest region into the northern Rockies, although pronounced relief from the water shortages will depend on the upcoming winter snow season. Less chance for drought relief is expected over the Great Basin and in much of Montana and eastern Idaho. In the Pacific Northwest, seasonal rains, especially during October-November, should ease the agricultural drought affecting the region. Seasonal rains are also expected to provide modest improvement for the drought affecting Hawaii.

Discussion for the Seasonal Drought Outlook

Tools used in the drought outlook included: the official CPC long-lead for the next 90 days, the Palmer Drought Index probability projections for the next 3 months, and various medium and short-range forecasts and models such as the 6-10 day and 8-14 day forecasts and the 2-week soil moisture forecast. Additional tools included the constructed analogue from soil moisture forecasts.

With weak signals from the various forecast tools regarding the Sep-Nov outlook for precipitation over most of the country, this forecast focuses on climatology, the constructed analogue soil moisture tool for November, and the near-term circulation trends as seen in the latest model runs.

The soil moisture analogue tool -CAS--implies a tendency for drought to persist in the South Dakota-Nebraska-northern Kansas area, and the short to medium-range forecasts have been showing only light rain in this area, so the odds favor persisting drought. The confidence is lower for the Missouri- southern Iowa area, as the CAS suggests improvement. But some of the statistical and dynamical tools used for the 90-day precipitation forecasts show a tendency for below-normal rainfall from the Great Lakes into Oklahoma, and available 10-day and 15-day soil moisture forecasts show drying in this area, so the odds favored persisting drought here as well. For the Minnesota-Wisconsin area, confidence is very low due to ambiguous or conflicting signals, but some indications of a pattern of ridging to the west and troughing to the east, and a resulting tilt toward below-normal rainfall, led to the forecast of persisting. There is also a seasonal tendency for rainfall to diminish as we go into November.

The area with limited improvement in the West is based on the CAS for November and medium range outlooks. Widespread thunderstorms are on tap for parts of the West in the next 1 to 2 weeks. More significant improvement is unlikely until we are well into the winter snow season. CAS and climatology suggest less improvement for much of Montana into the Great Basin. Climatology indicates improvement for Washington and Oregon, as precipitation is generally substantial by the end of November, especially in western areas. The improvement for Hawaii is also based on expected increased seasonal rainfall.

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: August 21, 2003
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