Midwest Weekly Highlights - September 15-21, 2005

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Midwest Dry Regions Receive More Rain

The Midwest stayed under an active weather pattern this week. Dry areas in the southern half of the region experienced several rainy days during the period, helping to ameliorate some of the drought in those areas. Large portions of southern Missouri and Illinois received 2-4 inches of rain, with 1-3 inches falling further north in central Illinois and Indiana (Figure 1). While most of the precipitation in the southern portion of the region was formed along warm and cold fronts, the low pressure centers themselves also dowsed the central Upper Peninsula of Michigan with 2-4 inches of rain, too. This area in Michigan, as well as a large swath from southwestern Missouri to eastern Ohio, received more than 200% of normal precipitation for the week (Figure 2). The week was above normal in temperature throughout the region, especially in the northern Midwest, which was 5-8°F above normal (Figure 3). At the end of the week, all eyes turned to Hurricane Rita in the Gulf of Mexico (Figure 4, NOAA). Rita became a major hurricane on the 21st, capable of causing catastrophic damage to the Gulf Coast around the 24th; some moisture from this storm is expected to eventually end up in the Midwest during the next reporting period.

September 19 Severe Weather Outbreak

A low pressure center moved quickly into the region on the morning of September 19, trailing a strong cold front (Figure 5, College of DuPage - COD). As the day progressed, and upper level winds became more favorable, a long line of thunderstorms broke out ahead of the front (Figure 6, COD). For a time, a squall line hundreds of miles long stretched from eastern Kansas to western Indiana (Figure 7, University Corporation for Atmospheric Research), before it broke into clusters of strong storms in both Missouri and Illinois. Heavy rains accompanied a large number of severe wind and hail reports through the region (Figure 8, Storm Prediction Center). Precipitation totals were largest in an area south of the mid-point of the extreme drought area in Iowa (Figure 9a, National Weather Service - NWS), Missouri (Figure 9b, NWS), and Illinois (Figure 9c, NWS). In Missouri, about 58,000 lost power during the storm in the St. Louis area alone, and in Illinois, thousands lost power in central and east-central parts of the state. Injuries were also reported when several vehicles were swept off the highway by high winds, but no deaths occurred. The period ended with a return to warm and sunny conditions on the 21st, but more active weather was expected for next week, as another front and the remnants of Hurricane Rita are expected to visit the area (Figure 10, Tropical Prediction Center).