Hail in the Vicinity of Organized Updrafts

Abstract

Several encounters with hail and graupel (often inadvertent) have occurred while flying an aircraft through the organized updrafts at the base of thunderstorms in the High Plains area. These encounters normally occurred while entering or exiting the organized updrafts and while flying in the vicinity of the strong horizontal reflectivity gradients which commonly border organized updrafts. On several occasions mobile ground crews were beneath the organized updrafts and confirmed the observations from the aircraft. These crews also noted the sequence of precipitation events in this region. The hail which falls in this particular region has the following characteristics: it has a narrow size range, it is large hail (often the largest which falls from the storm), it is commonly not accompanied by rain, and it has a small range of concentrations for a given diameter. The precipitation sequence at the ground over which an organized updraft passes is large hail followed by smaller hail and rain.