Insights from Composite Environments of High-Shear, Low-CAPE Severe Convection

Recent work has shown that severe high-shear, low-CAPE (HSLC) convection tends to occur in environments with stronger synoptic-scale forcing for ascent and larger low-level instability and vertical wind shear vector magnitude than its nonsevere counterpart. Additionally, analyses and simulations of HSLC severe events show that rapid destabilization resulting from the release of potential instability and/or strong low-level theta-e advection may enhance apparently limited CAPE values on temporal (and potentially spatial) scales unresolvable by most numerical weather prediction models.

This presentation supplements these recent findings with storm-relative composite maps and soundings from 2006-2014 HSLC severe report subsets segregated by report type, convective mode, and event severity. In addition, these composites will be compared to composite environments of false alarm tornado and severe thunderstorm warnings and radar-based nulls. The goal of this work is to improve pattern recognition of HSLC severe convective events by presenting the typical spatial arrangements of several environmental ingredients. The ultimate aim is to increase (decrease) the associated relatively low (high) probability of detection (false alarm rate) of NWS tornado watches and warnings within HSLC environments by comparing severe event composites to those of nonsevere events.