A Giant Hailstone from Kansas in Free Fall

Abstract

Replicas of a hailstone that weighed 766 gm and which had large spikes confined mainly to one side were dropped from heights of up to 900 m and also tested in a wind tunnel to determine the hailstone's aerodynamic properties. It was concluded that the critical Reynolds number was not quite reached by the replicas during free fall, but that the original hailstone (due to denser air at a lower ground level) probably did enter the supercritical regime shortly before impact. Its speed on reaching the ground is therefore concluded to have been about 47 m sec?1. Its fallspeed proved to be nearly independent of hailstone attitude. It must have undergone oscillations during descent but in a manner such that the spiky side did not face downward.