Earth and Atmospheric Sciences, Department of


First Advisor

Adam Houston

Date of this Version

Summer 7-29-2022


Axon, Kristen L., "Using Remote and In Situ Observations from TORUS to Investigate a Preexisting Airmass Boundary and its Influence on a Tornadic Supercell on 28 May 2019" (2022). Dissertations & Theses in Earth and Atmospheric Sciences.


A THESIS Presented to the Faculty of The Graduate College of 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: July 2022

Copyright © 2022 Kristen Lauren Axon


During the 2019 field phase of Targeted Observation by Radars and UAS of Supercells (TORUS), a preexisting airmass boundary was sampled on 28 May 2019 in north-central Kansas in close proximity to a tornadic supercell. This work hypothesized that the preexisting airmass boundary was associated with a mesoscale air mass with high theta-E (MAHTE) that favorably interacted with the tornadic supercell to increase the likelihood of tornadogenesis. Observations from TORUS including mobile mesonets, unoccupied aerial vehicles, soundings, and ground-based mobile radar were used along with GOES-16 visible satellite imagery, Kansas mesonet surface stations, and KUEX WSR-88D data to investigate this hypothesis.

Analysis revealed that the preexisting airmass boundary was associated with a synoptic-scale warm front and the cool air mass associated with this boundary had higher moisture compared to the warm side environment resulting in a higher equivalent potential temperature within the cooler air mass. This MAHTE had a boundary-normal width of around 13 km and a vertical depth around 400 m meaning it was truly mesoscale in size. The environment within the MAHTE had similar MLCAPE, greater vertical wind shear, and a lower lifting condensation level than the warm side environment rendering it more favorable for tornadic supercells.

A storm-scale analysis of the evolution of the tornadic supercell, a nontornadic supercell that developed within the MAHTE to the northeast of the tornadic storm, and the preexisting airmass boundary indicated that the preexisting airmass boundary likely interacted with the tornadic supercell in a way that promoted tornadogenesis. The nontornadic supercell also produced at least two outflow boundaries that interacted with the tornadic storm, one of which had a very stable air mass behind it and is hypothesized to have weakened the tornadic supercell.

Advisor: Adam L. Houston