Temperature and Precipitation Anomalies.
The Midwest was dry most of the month until the remnants of Tropical Storm Isidore drenched Kentucky and the lower Ohio Valley, helping to ameliorate drought in those regions. The Midwest as a whole went from being in one of the driest Septembers on record to merely the 41st driest, while Isidore gave Kentucky its 5th wettest September. The plume of tropical precipitation entering the eastern Midwest brought monthly totals up to 5-10 inches in places (Figure 1). Meanwhile, much of Missouri, east central Illinois, and Lower Michigan received very little rain, missing both Isidore and a variety of clipper systems catching the northwestern Midwest. These dry areas received less than 50% of normal precipitation for the month (Figure 2). September 2002 was warmer than normal throughout the Midwest, the 13th warmest overall since 1895. Far western Midwest locations were 1-3°F above normal for the month, while much of the eastern and northern Midwest was 4-6°F above normal (Figure 3). The combination of heat and lack of rain caused drought to expand and intensify by the end of the month in northern Missouri and Lower Michigan, while conditions improved markedly in Kentucky and the west and central parts of the Ohio Valley (Figure 4).