An Analysis of High Frequency Radar Measurements of Spatiotemporally Varying Low-Level Vertical Wind Shear Near Supercells from the TORUS Campaign

The role of vertical wind shear in mesocyclone development and tornadogenesis has been increasingly studied in recent years due to the multitude of field projects centered around observing severe weather. Many field projects utilize radiosondes for collecting data on the instantaneous vertical wind shear of the environment, but due to the nature of radiosonde launching, obtaining a resolute depiction of the spatiotemporal evolution of vertical wind shear within the inflow of mesocyclones is difficult. Due to this, much of the research conducted on vertical wind shear does not contain a highly resolute spatiotemporal element, which could provide further insight into the impact of vertical wind shear on the evolution of vertical vorticity and updraft intensity throughout their life cycles.

While radiosondes are still essential for in-situ measurements of vertical wind shear, mobile Doppler radars can also be used for this purpose. In this study, two Texas Tech University Ka-band (TTUKa) mobile Doppler radars were used to collect low level velocity azimuth display (VAD) data of supercell environments at a comparatively higher spatial and temporal resolution than radiosondes. With this data, the environment the updraft is ingesting, how this affects the mesocyclone intensity, and possibly how the supercell modifies its own environment can be directly observed.

Over 5,000 VADs will be considered in this study, captured within the inflow of supercells during the Targeted Observations by Radars and UAS of Supercells (TORUS) project in 2019 and 2022, and the TORUS-Left-flank Intensive Experiment (TORUS-Lite) in 2023. VADs examined by this study were determined to be within the inflow of the supercell via a position to the right of the storm motion, calculated by the change in position of the greatest azimuthal shear value, a product derived from the Multi-Radar Multi-Sensor (MRMS) database. VADs were then analyzed according to several different criteria including whether the target storm was tornadic, the time the VAD was taken relative to tornado production, and the lowest-level mesocyclone intensity and trend. Composite hodographs were generated for each of these subsets and compared.

Initial results show that, similar to recent studies, the low-level shear for tornadic storms was greater in both magnitude and curvature. We will expand on these initial findings at the conference and highlight specific examples, such as the tornadic supercell observed on May 23, 2022, in Morton, Texas.