A Remarkable Thunderstorm Flight Record

Abstract

The barogram of a sailplane flight in a thunderstorm at Benalla, Victoria, shows a descent from an altitude of 12,400 ft. to the sulfate at velocities exceeding 300 ft./sec. over a large part of that height range. The record and the meteorograph used were examined In detail, without definite evidence of instrumental failure. Flight trials gave 100 ft./sec. as maximum descent velocity for the sailplane, while the aerological conditions suggest an upper limit of 130 ft./sec. for the downdraft itself. In comparison with similar data obtained in Florida thunderstorms the lognormal distribution of these data is used to estimate the probability of various large downdraft velocities.