18th Conference on Weather and Forecasting, 14th Conference on Numerical Weather Prediction, and Ninth Conference on Mesoscale Processes

Thursday, 2 August 2001
Radar characteristics of severe wind-producing convective systems over the Northern High Plains
Brian A. Klimowski, NOAA/NWSFO, Rapid City, SD; and M. R. Hjelmfelt
The availability of NEXRAD data across the conterminous United States has allowed for the study of convection over much broader spatial and temporal domains than ever before. This research takes advantage of the availability of NEXRAD data in identifying the radar characteristics of a broad spectrum of convective storms: severe wind-producing systems. Over the four convective seasons from 1996 through 1999, all severe wind-producing convective systems and squall lines over the Northern High Plains (roughly from the Central Dakotas west to the Rockies) were documented, and radar data analyzed. Over three hundred such convective systems were studied over this four year period. For these cases, NEXRAD radar data was analyzed in order to classify the morphology of each convective event and assess its’ evolutionary characteristics. Environmental soundings were also analyzed in order to determine the atmospheric conditions associated with the formation of these systems.

The research to be presented essentially addresses the question: “What are the radar characteristics of, and differences between the environments which produce severe wind-producing squall lines, bow echoes, supercells, and weakly-organized convective systems over the Northern High Plains?”

Preliminary analyses of this large data set indicate several interesting results. Firstly, a very large percentage of all high wind reports (>85%) originated from organized convective systems (squall lines, bow echoes, and supercell thunderstorms), not isolated downburst or microburst activity. Secondly, of all the storms which were initiated over the Northern High Plains, very few of them (less than 6%) maintained their structure long enough to move east of the study area (i.e. moved out of the Northern High Plains) - inferring that the observed diurnal progression of convection east of the Rocky mountains may be more complicated than previously thought. Thirdly, a distinct ‘corridor’ of severe wind-producing supercell storms was identified. Analyses of these results will be presented.

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