An Empirical Examination of the Environmental Factors That Regulated Thunderstorm Longevity on 22 May 2019 in Oklahoma

This study examines whether any environmental measures which influence the physical processes relating to storm longevity can effectively discriminate between shorter and longer-lived convection. Over 100 sounding-derived parameters using Rapid Refresh (RAP) model analyses were obtained for all surface-based deep convection that formed on 22 May 2019 in Oklahoma. This event was characterized by a favorable environment for supercells and tornadoes across a relatively broad area, resulting in the issuance of two PDS tornado watches. While deep convection initiated in multiple locations within this environment, significant differences in storm longevity and severity were notable across 3 different subdomains identified in the analysis: near the dryline, the open warm sector, and near the warm front.

The statistical distribution of the parameters examined in the study was based on multiple different comparison types, including storm longevity (in minutes), convective mode (supercells vs. non-supercells), the association of severe reports and tornadoes, whether storms were discrete or clustered, and the distance to other storms. The longest-lived storms during the event were supercells, and the most consistent environmental signals found in the analysis were related to comparisons involving supercells and longer-lived storms. These supercells and long-lived storms were characterized by having lower (but sufficient) measures of instability and low-level lapse rates, higher low-level moisture content and lower lifting condensation levels, higher convective inhibition and higher levels of free convection, stronger 0-1 km storm-relative helicity and bulk wind-difference, and slower storm motion that deviated more to the right. An examination of the spatial distribution of these ingredients throughout the course of the event indicated that longer-lived supercells tracked along relatively substantial gradients in many of the parameters that had the most notable statistical differences. Moreover, there are indications that favorable values of moisture and low-level shear seemed to come together "just in time" as longer-lived storms tracked into those environments.