Severe weather reports as a function of convective system morphology

An earlier climatological study to examine the distribution of severe weather reports as a function of convective system morphology has been expanded to include more of the warm season of 2002, along with the inclusion of a larger sample of linear systems having line-parallel and leading stratiform rain. All convective systems occurring from April 1 through August 31 of 2002 were classified into 9 morphologies using NOWRAD composite data available via a UCAR archive. The morphologies included individual cells, clusters of cells, broken lines, nonlinear systems, bow echoes, and four types of linear systems, those with no, leading, line-parallel, and trailing stratiform rain. In total, over 925 separate storm systems were identified, with nearly 10,000 severe weather reports associated with them. Although many of the results were similar to those found in the earlier study which generally concentrated on the summer months of 2002, the inclusion of extra line-parallel and leading stratiform linear systems, identified by Parker and Johnson, to triple the available sample, led to some changes in results.

Linear systems were most likely to have at least one severe report associated with them, with every leading stratiform and no stratiform rain system having at least one report. Cellular storms had the lowest frequency, despite being associated with the most severe weather reports, a result reflecting the large number of cases, and the small-size of these events. Marginally severe hail was found to be most common in bow echoes and broken lines, while larger hail was most common in cellular systems, broken lines, and linear systems having line-parallel stratiform regions. As might be expected, severe wind reports were most comon by far in bow echoes, with a rate more than double that of any other morphology. The morphology with the next highest frequency of wind reports was linear systems with trailing stratiform rainfall, possibly reflecting the role of the rear-inflow jet in these cases. Flooding events were concentrated in linear systems with trailing or line-parallel stratiform rainfall, and in broken lines. Tornadoes were most common in broken lines and linear systems with line-parallel stratiform rainfall.