The Scales of Hail

Abstract

The first climatic investigations of hail in North America were by Lemons and Flora during the 1940's. These were followed by more intensive, state-scale climatic investigations in the 1960's to meet insurance concerns. Subsequent concerns with hail by the aviation industry and the weather modification community led to the first collection of mesoscale hail data from dense networks and radar studies during the 1960's and 1970's. This paper is a review of available hail information presented in a series of time and space scales. Although the North American hail data and information are less than adequate, there is much more hail information than exists elsewhere in the world. Very extensive findings on hail are available for Alberta, Illinois and Colorado. Phenomenologically oriented studies have focused on hailstones, point hailfalls, hailstreaks, hailstorm, hailswaths and hail days over various sized areas. Results for each of these classifications are presented according to studies that focused on national, regional and small-scale areas. The principal hail area of the continent is in and to the lee of the Rocky, Mountains where hail is both frequent and intense; hence the Great Plains suffers great damages. Another high-frequency area related to spring storms extends from Texas to Michigan, but causes less crop damage since it largely precedes the crop season. Certain inexpensive data collection efforts and analyses which would greatly improve our knowledge of hail are recommended.