The 21 June 1997 Flood: Storm-Scale Simulations and Implications for Operational Forecasting

Abstract

Abstract On 20–21 June 1997, a convective outbreak in Nebraska, Iowa, Illinois, and Wisconsin resulted in two fatalities, eight injuries, and approximately $104 million in damage. The majority of the damage ($92 million) was the result of flooding in southeastern Wisconsin owing to nearly 250 mm of rain produced by training convection and to a lesser extent the passage of a persistent, elongated convective system. The flood event is analyzed and storm-scale (5- and 1.67-km grid spacing) resolution model simulations at 0–24-, 12–36-, and 24–48-h ranges are produced to study the evolution and predictability of the rainfall. Synoptic conditions corresponded closely to the mesohigh pattern frequently associated with heavy rainfall events. Despite the recognition by National Weather Service forecasters of the potential for heavy rainfall, uncertainty concerning event magnitude and affected areas, exacerbated by poor operational model guidance, resulted in a failure to issue flash flood watches prior to the ons...