The Morphology of Several Tornadic Storms on 20 May 1977

Abstract

Sixteen tornadic storms occurred in the afternoon and evening hours of 20 May 1977 and the early morning hours of 21 May 1977. Three storms, two of them tornadic, have been selected for detailed study. One of the tornadic storms was observed for 2 h during its growth stage prior to becoming tornadic. Radar displays indicated that it merged with a more mature but intensifying storm to its north. After this apparent merger, the storm to the north dissipated and the southern storm continued to become more vigorous and eventually produced a tornado. These storms displayed common structural similarities to another tornadic storm which was observed during its mature stage several hours earlier. Despite differences in the environments in which these storms grew, they share a characteristic structure and evolution as can be determined by this sample of their lifetimes.