Possible Newly Recognized Meteorological Phenomenon called Crown Flash

Abstract

ON July 2, 1970, at about 1945 h EST a thunderstorm cell passed a few miles north of Ann Arbor, Michigan. The column of cumulus cloud towered in the light of the setting Sun, far above the dark mass below, which occasionally flickered with lightning. Thin lamellae of cirriform cloud began to form above the peak of the cumulus column and streamed off to the north-east, in advance of the storm cloud. The cumulus column impinged on these lamellae as it boiled upward, causing the horizontal layers of thin cloud to become somewhat dome-shaped in the region of the rising column (Fig. 1). At and just above the peak of the storm cell the cloud mass seemed to be undergoing sudden changes in brightness lasting for several seconds at a time. J. C. G.'s wife and two children also noticed the effect when it was called to their attention. M. E. G., a meteorologist, also verified the observation. The phenomenon continued to occur repeatedly at intervals of 30–60 s during the next 15 or 20 min, providing the basis for the following description.