Midwest Overview - September 25-30, 2002

The last six days of September were quite eventful in the eastern Midwest. The remnants of Tropical Storm Isidore dumped 3-5 inches over western Kentucky, southern Indiana, and southeastern Ohio (Figure 1). Some places received up to 6-8 inches of rain, causing localized flooding and resolving in one event a long standing drought situation. Except for Isidore, most storm systems ended up staying well to the north between September 25 and 30. While 1-3 inches of rain were recorded in eastern Minnesota and northern Wisconsin, a wide swath from Missouri to northeastern Lower Michigan received nothing at all. A strong gradient existed at the edge of the Isidore impacted area, between 300-600% of normal precipitation and less than 25% of normal precipitation for the period (Figure 2). Clouds and showers in the northwestern Midwest kept temperatures 1-3°F below normal in Minnesota and adjacent areas, while most of the southern two-thirds of the region was 2-4°F above normal (Figure 3). Drought status changed radically in some areas this week (Figure 4, National Drought Mitigation Center), with some locations improving from severe drought (D2) status on the U.S. Drought Monitor to D0, or even normal non-drought status in the western Ohio Valley. Unfortunately, moderate drought status expanded in Lower Michigan, and severe drought entered north-central Missouri, the areas received no rain.

Very little storm damage occurred in the Midwest during the passage of Isidore on the 26th and 27th, although local flooding was common in Kentucky and other parts of the Ohio Valley. The edge of the rain shield was very abrupt (Figure 5, National Weather Service (NWS)), and a dense layer of tropical cirrus attenuated the sun considerably over the east-central Illinois site of the MRCC. Radar rain totals exceeded 10 inches in some locations (Figure 6a, Figure 6b, and Figure 6c, NWS), and a distinct plume of moisture could be seen all the way from the Gulf coast to southwestern Ohio (Figure 7).