Influence of Wind Shear on the Growth of Hail

Abstract

Dessens (1960) has suggested that strong winds aloft favor the growth of hail in thunderstorms building under their influence. The physical implication of this suggestion is examined by making computations on the growth of hailstones in a model cloud under vertical wind shear. The computations are based essentially on the Schumann-Ludlam formulation of the hail problem. The model cloud has been hypothesized for the mean hail sounding in the Denver area published by Beckwith (1960). The conclusions indicated by these computations are that (1) there is a higher probability of hail in thunderstorms formed under strong vertical wind shear than those without shear; and (2) the maximum size attainable by hailstones is greater in a cloud without shear than in one under shear, provided that the strength of the updraft, the vertical distributions of liquid water content and temperature are the same in the core of the two clouds. It is also indicated that in the absence of vertical shear the updrafts required for the formation of large hailstones need to be decelerated near the top of the liquid water cloud so as to prevent the hail embryos from being blown out into the glaciated portion of the cloud.