Midwest Overview - July, 2003

---

The month of July 2003 was quite eventful in the Midwest. An intense ridge formed over the western United States, leaving the Midwest in a northwest flow pattern for most of the month (Figure 1, Climate Diagnostic Center). The mean trough over the Midwest formed a boundary between cooler, drier air and warmer, moister air, as is common during the spring. Wave after wave of severe weather events took place throughout the month, centered on Indiana and Ohio but at various times impacting all the states in the region. The worst damage, however, was due to flash flooding and river flooding from the heavy rains accompanying the severe weather events. Precipitation totals commonly exceeded 10-12 inches for July in Indiana (Figure 2), with the entire state averaging approximately 200% of normal precipitation for the month (Figure 3). Indiana had its second wettest July on record, while Ohio had its fourth wettest July on record. The same western ridge that has brought about troughing and precipitation in the central and eastern Midwest influenced Missouri to be very dry, with most of the western part of the state receiving less than 50% of normal precipitation. The Kansas City International Airport set a new record for its driest July, recording only 0.12 inches of precipitation. Missouri as a whole had its 33rd driest July in the last 109 years. Missouri was also the only state in the Midwest with above normal temperatures for July 2003, while most of the rest of the region experiencing temperatures 0.5 to 2.0°F below normal (Figure 4). The warm and very dry conditions caused moderate drought to extend into most of western Missouri by the end of the month (Figure 5, National Drought Mitigation Center).