A climatology of severe weather reports as a function of convective system morphology

Radar data and Storm Data storm reports from 10 states in the U.S. Central Plains were used to determine the distribution of severe weather reports as a function of convective system morphology during the period May 15, 2002 through August 31, 2002. Radar data were used to define morphologies including individual cells, clusters of cells, non-linear convective systems, squall lines, broken squall lines, squall lines with trailing, line-parallel, or line-forward stratiform rain regions, and bow echoes. Tornado reports, damaging winds of two intensity levels, flash flooding, and hail reports in three size ranges were classified.

As would be expected, the most prolific producers of tornadoes were individual cells and clusters of cells, although a surprisingly high number were found in non-linear convective systems. Normalized on a per case basis, however, broken lines dominated. Squall lines with line-parallel stratiform regions had the most reports per case of floods, followed by lines with trailing stratiform rain. Surprisingly, squall lines with line-parallel stratiform rain had the most reports of giant hail (greater than 2 inch diameter) per case, but they were limited in number so the results may not be robust. Cell catagories generally dominated for giant hail. Marginally severe hail was most common on a per case basis in bow echoes and line-forward squall lines. Not surprisingly, bow echoes produced the most cases of severe wind, followed by squall lines with trailing stratiform rain and nonlinear convective systems.