A Composite Analysis of Winter Season Overrunning Precipitation Bands over the Southern Plains of the United States

Abstract

This investigation presents an extensive analysis of precipitation bands associated with winter season ?over-running? events in the southern plains of the United States. The primary motivation is an investigation of the relevance of conditional symmetric instability (CSI) theory to overrunning precipitation events. This is accomplished by means of a statistical composite study of events of differing degrees of bandedness, using synoptic sounding and National Weather Service radar data. The composite study shows that it is difficult to distinguish between the environments of banded and nonbanded cases on the basis of individually examined shear and buoyancy parameters. Some statistically significant differences do occur when shear and buoyancy effects are combined in an evaluation of CSI, with more strongly banded events showing greater instability.