Numerous supercells developed along a stationary/warm front in southeast Iowa and west central Illinois, from about the Louisa/Henry/Des Moines County borders east into Mercer county in the early evening. Activity initiated as single cell moving from Wapello County around 5 pm that tracked into Jefferson County and produced large hail. Several supercells formed and tracked over the same areas of southern Louisa into southern Mercer Counties into the evening with widespread golfball to baseball size hail reports, funnel cloud sightings and rain wrapped tornado reports. Visibility was poor due to considerable haze in airmass. Event continued well after sunset with one main supercell moving from Mercer County into southern Henry County Illinois into Bureau and Putnam Counties. Between 8 and 10 pm, several storms with smaller, but severe hail continued along the front in southeast Iowa through late evening. Isolated elevated severe hail producers continued late evening from central Iowa into eastern Iowa. Also of note was excessive rainfall amounts in areas that had repeated supercells, resulting in widespread rural flooding and some reports of deep/drifting hail.
Two teams from the national weather service conducted damage surveys on May 1 2003. The teams confirmed 5 tornadoes from Louisa County into Mercer County.
In Louisa County Iowa...
Tornado beginning near Morning Sun.
Time: 635 pm
Length: 16 miles
Width: .5 mile early on...then approximately 50 yards until dissipating southwest of New Boston
In Mercer County Illinois...
Tornado beginning 2 miles southeast of Aledo tracking east.
Time: 657 pm
Length: .8 miles
Width: 20 yards
Brief tornado 1 mile south of Viola.
Time: 708 pm
Length: .1 mile
Width: 50 yards
Tornado beginning .25 miles east of Viola.
Time: 711 pm
Length: .5 mile
Width: 25 yards
Tornado beginning .5 miles east of Viola.
Time: 712 pm
Length: .5 mile
Width: 75 yards
We would like to express our thanks to local officials and residents of Louisa...Mercer...and Putnam counties for their assistance and hospitality during the surveys. Also we are grateful for the timely spotter reports during the event from the entire area.