Storms of May 23, 2000

Overview: A significant severe weather outbreak occurred during the evening of May 23, primarily across the western Kentucky, southeast Missouri, and far southern Illinois  counties of the Paducah County Warning Area (CWA). A cold front moved slowly south across central Illinois and Indiana during the day, and by evening, it was approaching the lower Ohio Valley. Thunderstorms developed ahead of the front in a warm, humid, and very unstable air mass. Late in the afternoon, temperatures were well up in the 80s with dew points in the lower 70s. An essential ingredient for severe storms, wind shear, was present. Winds in the mid levels of the atmosphere were northwest at close to 50 knots. Closer to the surface, they were southwest at 20 to 30 knots. As a result, the Storm Prediction Center issued Tornado Watch 334 at 650 P.M. for much of western Kentucky. A short while later at 728 P.M., another Tornado Watch (Number 335) was issued for southern Illinois, southeast Missouri, and the rest of west Kentucky.

Radar Images and Storm Evolution: The first storms actually occurred earlier in the day, including an F-3 tornado at Leitchfield, Kentucky, just east of the Paducah County Warning Area. However, in the Paducah CWA, the most significant activity was mainly during the evening. Isolated supercells began forming around 6 P.M. Radar showed distinct signs of rotation with one of the first supercells. This cell formed rapidly just east of Paducah, then moved southeast across Marshall County into Calloway County. The radar image below shows the storm along the Calloway/Marshall County border at about 6:30 P.M. Notice the hook-shaped feature between Murray and Benton, along the Marshall/Calloway County border. This feature is commonly seen with tornadic storms.

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The next image below, which was taken just several minutes prior to the above image, shows atmospheric motion in the storm. Rotation is depicted by the red/green couplet. Notice the rotation coincides with the location of the hook-shaped radar echo. It was in this location, near Almo along the Calloway/Marshall County line, that storm surveys revealed an F-1 tornado touched down. Damage to roofs and trees occurred here. A funnel cloud was frequently observed with this storm from central Marshall County near Benton to the Tennessee state line southeast of Murray. Sporadic wind damage reports were received all along the path of this storm, as well as large hail up to an inch and a half in diameter.

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Later in the evening, additional supercells began developing over southern Illinois. One cell that developed in the Carbondale area became a tremendous storm as it moved into Johnson County around 9:45 P.M. In the city of Vienna, along I-24 between Marion, IL and Paducah, baseball size hail fell around 10 P.M. The storm continued to frequently produce large hail as it moved southeast toward the Ohio River. As the storm approached the Ohio River just northeast of Metropolis, IL, rotation in the storm increased, and Tornado Warnings were issued for Massac and Pope Counties in Illinois. A funnel cloud was observed extending more than halfway to the ground.

The radar image below shows a radar product called VIL (Vertically Integrated Liquid). The VIL product is excellent for diagnosing the large hail potential of storms. The highest VIL values, over 70, are colored in white. On this day, VIL values over 70 corresponded to golf ball size hail or larger. The VIL values near Vienna at this time (9:46 P.M.) were actually in the 80s and corresponded to reports of baseball size hail. The correlation between VIL value and hail size depends on the thermal structure of the atmosphere. In winter, VILs as low as 35 can produce large hail, while in summer, VILs as high as 60 may not.

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These are just a couple of the most severe storms of the event. There were numerous other severe weather events on the 23rd, including baseball size hail in Scott County, Missouri.



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