Barron County, Wisconsin, Multiple Tornadoes and Hailstorms of 11 September 1990

Abstract

Four tornadoes, of F1?F2 intensity, occurred over Barron County, Wisconsin, on the evening of 11 September 1990. The tornadoes were associated with a slow-moving thunderstorm cluster that developed along a warm front, and all occurred within 17 km of Rice Lake over a 2-hour and 15-minute period. National Weather Service radar data indicate that the tornadoes probably were associated with mesocyclones. Hail up to 7 cm in diameter and damaging winds also were reported over Barron County and three adjoining counties. Forecasting of slow-moving thunderstorms within an environment capable of producing mesocyclones and tornadoes remains an important forecast problem. Analysis of features that produced quasi-stationary thunderstorms and a vertical wind profile sufficient to generate mesocyclones hopefully will improve recognition and forecasting of similar events in the future.