March 8, 2000

Earliest tornado on record for Milwaukee County

The Milwaukee tornado has been rated at the top of the F1 range with winds around 110 mph. The path length was 2.2 miles, and path width was about 75 yards. Sixteen (16) people were injured and there were no fatalities. Based on Milwaukee County Emergency Management documentation, total estimated public sector damage was $99,000 (including debris clearance), and total estimated private sector damage was $4,500,000. Fifty-three (53) residential homes sustained minor damage and 11 had major damage. Eight (8) businesses sustained major damage. Many motor vehicles were overturned, roofs were partially peeled off homes, power lines and trees were toppled, and gas leaks were reported.

The tornado briefly had multiple-vortex characteristics based on video tapes and eyewitness accounts. The parent thunderstorm moved quickly northeast at about 50 mph through eastern Walworth County, through western Racine County, and then directly northeast over the airport grounds. Brief, very heavy rains, isolated large hail (3/4 to 1 inch in diameter), and minor straight-line wind damage (downed trees) was noted by spotters in the forward flank downdraft (FFD) over Cudahy and St. Francis, preceding the tornado. The updraft tower and tornado were on the southern edge of the storm.

A severe weather spotter in Franklin, first noted cloud-base rotation and some semblance of a wall cloud at about 6:55 PM, when the thunderstorm was over extreme southwest Milwaukee County. This spotter attempted to relay his report to the National Weather Service Forecast Office near Sullivan (WFO MKX), but the report never made it to the office. However, Milwaukee/Sullivan's WSR-88D Doppler radar depicted the first mesocyclone in this thunderstorm at 6:55 PM. Spotter and airport control tower officials saw the first indications of a condensation funnel cloud over the southern part of the airport grounds.

The Storm Predication Center (SPC) in Norman, OK, issued Tornado Watch Number 78 for south central and southeast Wisconsin at 1:55 PM, with the watch in effect from 2:30 PM to 8:00 PM.

Synoptically, southern Wisconsin experienced record warmth during the afternoon hours. A deep surface low pressure moved northeast along the Mississippi River toward northern Wisconsin. Both Madison and Milwaukee registered record highs of 77 degrees prior to the arrival of a trailing cold front. A dry-line was noted from southwest Wisconsin down through western Illinois. Southeastern Wisconsin was dry-slotted as the jet stream punched northeast overhead. The southwest jet stream winds were 80 to 100 knots. Consequently, there was sufficient speed-shear in the atmosphere for isolated tornadoes.

WFO MKX meteorologists on duty at the time believe an outflow boundary was pushed northwestward to the Mitchell Field area by an earlier thunderstorm which clipped the southeast corner of Milwaukee County between 5:25 and 5:40 PM. There was also evidence of a lake breeze. This outflow boundary/lake breeze front may have helped focus low-level vorticity/circulations which later coupled with the mesocyclone aloft in the thunderstorm moving northeast out of western Racine County, resulting in a tornado. The meteorologists noted that several other thunderstorms over southern Wisconsin possessed radar-indicated mesocyclones that afternoon and evening. However, only one thunderstorm in northeast Dodge County was associated with a funnel cloud.

Tornado Images (click on images to enlarge)

Tornado Damage Images (click on images to enlarge)