Fall 2007 U.S. Drought Outlook and July to September Summary

Drought classifications are based on the US Drought Monitor. For a detailed explanation, please visit http://drought.unl.edu/dm/classify.htm. The outlook integrates existing conditions with forecasts from the National Oceanic and Atmospheric Administration’s Climate Prediction Center: http://www.cpc.ncep.noaa.gov/

Outlook: La Niña conditions are developing in the Pacific Ocean, so we anticipate that weather patterns will show a La Niña influence from the fall into next spring.  During a typical La Niña pattern, the Pacific Northwest and Ohio River Valley regions are wetter than normal, while the southwest and Gulf Coast regions are drier than normal. Based on the emerging La Niña pattern, drought should recede in the northern Rocky Mountains and northern Nevada and California.  Drought should also get less intense over much of the Tennessee and Ohio River valleys, the upper Midwest, the Gulf coasts of Alabama and Florida, and along the Great Lakes of New York.  Drought will probably persist in the desert southwest and in the Mid-Atlantic region.  Temperatures are projected to be well above normal for much of the United States through fall and into winter.  The warmest temperatures should be observed through the Southwest and Southern Plains, and into the Tennessee Valley. 

La Niña is named after a periodical cooling of the waters in the Pacific Ocean that influences weather patterns around the world.  For more on La Niña, please go to   http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml

July: During July, several new areas of drought developed, especially in the Midwest.  July started with 53.8 percent of the United States designated as abnormally dry or in drought, and ended with 64.1 percent.  Intensification of drought was prevalent in the western United States, where severe drought spread to include much of the region. Drought intensification over the High Plains and upper Midwest was observed during July.  With above normal temperatures and little or no precipitation, areas of South Dakota and Minnesota quickly deteriorated from no drought to severe drought. Drought became less intense in the Southeast as rains in Mississippi, Alabama and Florida helped make up precipitation deficits and ease impacts.  During July, almost 500 new drought impacts were recorded to the United States Drought Impact Reporter (http://droughtreporter.unl.edu).  Michigan, California, Montana and Alabama were the states where the most drought-related impacts were observed during the month. 

August: A heat wave over much of the southeastern United States coupled with below normal precipitation intensified drought in the Southeast.  Extreme and exceptional drought conditions covered much of the region by the end of August, with Alabama, Georgia, and Tennessee experiencing the most severe drought.  During August, the overall drought status for the United States improved.  August ended with 61.5 percent of the United States experiencing abnormally dry or drought conditions, compared to 64.1 percent at the beginning of the month.  Extreme and exceptional drought status increased from 6.8 percent to 12.8 percent during the month.  Reductions in drought intensities were observed over portions of the Midwest and High Plains and Southwest during the month.  More than 500 drought related impacts were logged into the Drought Impact Reporter.  North Carolina and Tennessee were the states logging the most impacts, at 66 and 49, respectively.

September: Warmer than normal temperatures dominated September, with most of the country having temperatures 2-4 degrees Fahrenheit above normal for the month.  The warmest temperatures were over the Midwest.  Precipitation amounts varied through the United States, with most areas receiving precipitation and a handful recording amounts above normal.  Overall drought conditions improved during September with 58.7 percent of the country depicting abnormally dry or drought conditions at the end of the month compared to 61.9 percent at the beginning of the month.  Extreme to exceptional drought conditions continued to dominate the Southeast, where some relief came in September.  The intensity eased in the upper Midwest while drought conditions continued to intensify over portions of western New York. 

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