Alec Prosser

Convective Meteorology (Mesoscale Dynamics)

Describing the Evolution of Background Wind Fields in Supercell Environments; a Radar-Based Investigation 

 Alec Prosser

Friday, May 3rd , 2024

NWC 1350 / 3:30 PM

Abstract: Numerous research studies over the past two decades have investigated the role of low-level wind shear upon both mesocyclone intensity and tornado likelihood in supercellular thunderstorms. A number of these studies suggest a strong connection between low-level storm-relative helicity (SRH) and likelihood of tornadogenesis, with shallow layers of SRH near the ground highlighted as a discriminating factor between tornadic and non-tornadic supercells. While this low-level SRH is a well-established factor in evaluating tornadogenesis likelihood, little attention has been given to the spatial and temporal evolution of this SRH in tornado-producing environments. To date, the limited number of studies concerning this evolution have emphasized that large differences in low-level SRH exist across the domain, and magnitudes of SRH increase considerably in proximity of supercell mesocyclones. Despite the utility of these low-level observations in discriminating tornadic and non-tornadic supercell environments, measuring the evolution is difficult to perform outside of campaigns designed to investigate the low-levels of thunderstorms (i.e., field campaigns). Additionally, the temporal resolution of observational datasets is somewhat limited, as many radiosonde-derived environmental wind profiles can only be completed once every hour. To address these limitations, many researchers turn to utilization of numerical weather prediction (NWP) to assess supercell environments. 
 
Utilizing radar offers a promising way to effectively observe the evolution of the near-storm wind field, using tools such as velocity azimuth displays (VAD), VAD wind profiles (VWP), or extended VAD (EVAD). These radar observations are more rapid (5-7 minutes per volume) than traditional wind field observations from soundings (~1 hour), and can help to offer insight into how swiftly the observed “near-field” background winds evolve in supercell environments. Though there are challenges related to avoiding convection-induced contamination in the VWP, performing calculations over smaller radii will help to mitigate contamination and allow for a higher resolution assessment of the environmental wind profiles near supercells. An exploration of the literature supporting the use of radar in this potential research avenue will be discussed, along with a brief “proof of concept” case from the 13 April 2019 Greenwood Springs, Mississippi tornadic supercell.