Date of Award

January 2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Atmospheric Sciences

First Advisor

Matthew Gilmore

Abstract

Supercell thunderstorms are among nature’s most powerful phenomena. Particular environmental conditions are strongly correlated with peak supercell and tornado strength. However, supercells may experience changes within the near-storm environment during their lifecycle. For example, a storm may cross a preexisting outflow boundary from previous convection; thus, the storm will experience changes in the environmental thermodynamic and wind profiles. The purpose of this study is to determine what happens to the low-level mesocyclone immediately after crossing a boundary, analyze storm sensitivity to differing boundary crossing times, and show how the vorticity processes change as a storm moves from one environment to another.Â

 An idealized cloud model is modified to simulate a heterogeneous environment in which there is a preexisting cold pool. A storm is initiated on the warm side of the boundary and crosses into the cool side. The low-level mesocyclone is analyzed as it crosses the boundary and Lagrangian trajectory analysis is performed to determine how vorticity is processed before and after crossing. This study finds that the low-level mesocyclone is cut-off as the preexisting boundary crosses the storm updraft; therefore, the low-level mesocyclone must reorganize on the cool side of the boundary. The environment on the cool side of the boundary is more conducive for low-level rotation but a stronger capping inversion may alter how vorticity is processed.

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