An Empirical Examination of the Environmental Variability that Impacted Supercell Evolution, Longevity, and Severe Weather Production on 22 May 2019 in Oklahoma

Authors

Kyle D. Pittman, University of Nebraska-LincolnFollow

First Advisor

Adam L. Houston

Date of this Version

11-2023

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Earth and Atmospheric Sciences

Under the supervision of Professor Adam L. Houston

Lincoln, Nebraska, November 2023

Comments

Copyright 2023, Kyle D. Pittman

Abstract

Mesoscale environmental heterogeneity can have significant impacts on thunderstorm organization, evolution, longevity, and severe weather production. This study examines the 22 May 2019 thunderstorm event in Oklahoma, where a relatively broad area of strong instability and vertical wind shear existed along a synoptic boundary and in the open warm sector that would seem to support long-lived supercells and tornadoes. There were two particularly dangerous situation (PDS) tornado watches issued during the event, but few severe reports and no tornadoes formed in the watch that covered the southwestern portion of the state. Several tornadic supercells and many more severe reports occurred in the watch that was present in the northeastern part of Oklahoma. This study introduces a viable analysis method to examine the differences in near-storm environmental characteristics between these areas using analysis data from the High-Resolution Rapid Refresh (HRRR) model.

The most notable environmental differences in this event were between western and eastern parts of the open warm sector. Both areas had values of low-level bulk wind difference, low-level storm relative helicity, lifted condensation level height, and significant tornado parameter values that were within the expected climatological range for significantly tornadic supercells. There were several rounds of convection initiation in both portions of the warm sector, but a more prominent “veer-back-veer” pattern in the low-level hodograph, combined with the reduction in mid-level buoyancy and drier mid-level conditions (associated with an elevated mixed layer) appeared to substantially limit supercell development in the western part of the warm sector, despite the favorable parameter space.

Advisor: Adam L. Houston