Characteristics of Hailstorms of Western South Dakota

Abstract

An extensive observational program has resulted in a description of the typical hailstorm of western South Dakota. The typical storm is cellular with new cells developing on its southwest side. The median hailstorm produces radar echoes to 12.2 km MSL and has a total up-air flux just over 1011 gm sec?1. Mean moisture inflow is around 109 gm sec?1, and precipitation efficiencies vary widely. Air and moisture fluxes in large storms exceed those in the median storm by a factor of 10. Maximum observed equivalent X-band radar reflectivity factor in the median hailstorm is 104.8 mm6 m?3 and occurs at ?5.5 km MSL. While there is evidence of occasional large steady-state cells characterized by very strong updrafts, hard hail and low precipitation efficiencies, most large storms pulsate as convective cells form and dissipate within them. Numerical models of hail-producing cells in the northern Great Plains should include time-dependent models capable of modeling the brake imposed on the updraft by precipitation.