May 2011 temp departures Precip percent of normal
Streamflow Tornadoes

Midwest Overview - May 2011

A Fickle May

Average daily temperatures during May ranged from 1°F to 3°F below normal in the western half of the region, to near normal to 2°F above normal in the eastern half of the region (Figure 1). However, this does not really tell the story of temperature variability during the month. The first week of May was generally much cooler than normal across the region, while the second week was much warmer than normal. The third and fourth weeks exhibited a pattern much like that for the month - cooler in the west, and warmer in the east.

Most of the Midwest received normal to above normal rainfall, with the exception of Wisconsin and the Arrowhead of Minnesota, where precipitation was about 75 percent of normal (Figure 2). Rainfall was heaviest from southern Missouri through the Ohio Valley and into the southeastern Great Lakes. The persistent wet weather in this area had a significant impact on spring planting progress. At the end of the month Ohio reported only 19 percent of corn planted, compared to an average of 93 percent, and 7 percent of soybeans planted compared to an average of 76 percent. Planting was also well behind in Indiana and Kentucky. In contrast, Iowa spring planting, which was far behind the normal pace in April, managed to surge ahead of the typical progress in early May with 84% of the corn and 47% of the soybeans planted during the first two weeks of the month according to Iowa Agricultural Statistics.

Major Flooding Subsides

Record flooding on the Ohio River and major flooding on the Mississippi River due to heavy spring rain, and in the case of the Mississippi River, snow melt, gradually subsided during the month. The peak of the flooding for the Midwestern states occurred the first few days of the month. However, stream flows at the end of May were still above normal across the region (Figure 3), and some minor to moderate flooding was still occurring on the Mississippi River, the Illinois River, and Wabash River due to heavy rain the last 10 days of the month.

Severe Weather in High Gear

Severe thunderstorms covered the region this month with no state left untouched (Figure 4), and all nine Midwestern states reported tornadoes this month (Figure 5). Storms were frequent in the central and eastern portions of the region. Severe storms were most numerous the last ten days of the month, starting with a major outbreak of severe weather on May 22nd. Joplin, MO took a direct hit by an EF5 tornado that resulted in a 14-mile path of devastation, killing 138 people and injuring 1,150 others. The multiple vortex tornado touched down just outside the western city limits of Joplin at 5:41 p.m. and rapidly intensified to an EF-5 tornado (>200 mph) within a few miles of initial touchdown. As the tornado tore through the city, at less than 10 miles per hour, it left a 0.75 to 1-mile wide path of destruction. The tornado weakened to EF-2 intensity near the eastern city limits, turned southeast and crossed  Interstate 44, eventually lifting 3 miles northwest of Diamond, MO.  The total path length was 13.8 miles. Nearly 7,000 homes were destroyed in addition to many businesses, churches, schools, a nursing home, a bank and one of two major hospitals in the area. Estimates indicate that nearly 30% of Joplin was damaged or destroyed. This tornado ranks as the deadliest single tornado on record for the state of Missouri.

Another tornado touching down in Minneapolis, MN on May 22nd resulted in one fatality.

Another outbreak of severe weather occurred on May 25th mostly in the southern half of the region. There were more than 1,000 severe weather reports that day, with the majority of those in Missouri, Illinois, Indiana, Kentucky, and Ohio.

Wet Spring in the Ohio Valley

Precipitation for meteorological spring (March, April, May) was 200 percent of normal from southwestern Missouri through the Ohio Valley (Figure 6), and 150 percent of normal from southern Missouri through southern Illinois, Indiana, and Ohio. Over the remainder of the Midwest precipitation ranged from 100 to 150 percent of normal, except for far western Missouri and southwestern Iowa, where precipitation was around 75 percent of normal. There were no areas of drought depicted in the Midwest at the end of the month on the U.S. Drought Monitor.

Temperatures during the spring ranged from 5°F below normal in western Minnesota to 1°F to 2°F above normal in the Ohio Valley (Figure 7).

For more details on weather and climate events during May 2011, click on the individual weekly report links on the upper right.

The Iowa State Climate Office and Missouri State Climate Office also contributed to this report.


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