Tornado and Hail in Wisconsin, March 8, 2000

After several days of record-breaking warmth, the stage was set for an out-of-season severe weather outbreak across southcentral and southeast Wisconsin. The city of Milwaukee recorded it's earliest tornado ever (just before sunset), and an extremely large number of reports of large hail from 3/4 to 1.75 inches in diameter were relayed to the NWS Sullivan office. Most of the thunderstorms developed gusty winds on the order of 30 to 50 mph, but one managed to generate a gust of 58 knots (67 mph) at the TV-4 station on the north side of Milwaukee. The thunderstorm which dumped large hail 7 N of Portage also had winds that uprooted some trees and blew a car off of Inerstate 39. An earlier thunderstorm that affected the west side of the city of Portage left the ground white with golf-ball size hail that also shattered several vehicle windshields. The thunderstorm that affected Wisconsin Dells also left the ground white with hail. The Milwaukee tornado spun up about 1/2 mile east/northeast of the terminal building of General Mitchell International Airport, just east of Runway 19, moved northeast and crossed East Layton Avenue just east of South Pennsylvania Avenue in Cudahy, continued northeast through St. Francis, and dissipated over the northwest corner of Nathanael Greene Park. Apparently the tornado wasn't strong enough to cause any damage on the airport grounds, but it did cause considerable damage in Cudahy and St. Francis. Fifty-three (53) residental homes sustained minor damage and eleven (11) had major damage. Eight (8) businesses sustained major damage. Many motor vehicles were over-turned, several roofs were partially peeled off of homes, power lines and trees were toppled, and gas leaks were reported. Sixteen (16) people were injured enough to require medical treatment (lacerations), but there were no fatilities. Most of the people who were injured were in their vehicles. Based on this damage, it is estimated that maximum wind speeds of this tornado were 105 to 110 mph. The airport terminal building and control tower went on emergency power after commercial power was disrupted. Airport control tower officials were able to divert airplane traffic, consequently there were no aircraft mishaps. Preceding the tornado, there were reports of large hail and some tree damage in the forward flank downdraft of the parent thunderstorm over St. Francis and the southern part of the city of Milwaukee. The tornado was extensively photographed and captured on video tape. It briefly displayed multiple-vortex characterisitics. The last time a tornado was documented in Milwaukee County was in May, 1989.NWS Sullivan meteorologists speculate that an outflow boundary was pushed northwest to the airport area from a thunderstorm that earlier moved through the southeast corner of Milwaukee County. This outflow boundary may have focused low-level vorticity that helped generate the tornado. The parent thunderstorm possessed a mesocyclone. Synoptically, a deep low pressure was moving northeast through central Iowa toward northern Wisconsin. This movement put southern Wisconsin in a "dry slot" associated with strong jet stream winds aloft. The combination of surface dewpoints in the lower to mid 50s, strong speed shear between surface winds out of the south and southwest mid-level winds, sufficient instability due to daytime heating/temperatures in the 70s, and cold air aloft allowed thunderstorms to grow to 40,000 feet. Several thunderstorms had supercell characturistics, but only one was assoicated with a tornado, and another with a funnel cloud. Thunderstorm movement was northeast at 50 to 60 mph (about 47 to 51 knots).