The Spatial, Temporal, and Thermodynamic Characteristics of Southern-Atlantic United States Tornado Events

Abstract

Tornadic storm environments are not well understood in regions beyond the Great Plains. Severe weather forecasting index values are derived for 129 Southern-Atlantic (SA) Coast (South Carolina, North Carolina, and Virginia) and 98 southern Great Plains (Texas, Oklahoma, and Kansas) tornado days through spatial and temporal interpolations of the proximity balloon soundings. Analyses of these data suggest that the two regions are associated with significantly different environments. The SA storm environments would be considered benign by Great Plains standards. In fact, 95% of the SA tornado events fall below the threshold for severe thunderstorms for the Severe Weather Threat (SWEAT) index. Therefore, the universal use of index threshold values by forecasters is inappropriate. Cluster and density analysis of the spatial data found that tornado events in the SA region are clustered in three general regions. One of the regions is likely influenced by the existence of a Sea-Breeze front or the Piedmont trough. However, given the benign thermodynamic environment, mesoscale augmentation of shear and instability is likely in the other two clustered regions as well.