Radar Precursors to Severe Weather Reports in Left-moving Supercells

Authors

Eric A. Carothers, University of Nebraska-LincolnFollow

First Advisor

Matthew S. Van Den Broeke

Date of this Version

5-2025

Document Type

Thesis

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 Matthew S. Van Den Broeke

Lincoln, Nebraska, May 2025

Comments

Copyright 2025, Eric A. Carothers. Used by permission

Abstract

While much research has examined dual-polarimetric signatures of right-moving supercells, very little has been done with left-moving supercells. Given that left-moving supercells are thought to be disproportionate producers of large hail, understanding their internal dynamics is vitally important. This study examines differences and trends in the dual-polarimetric signatures of left-moving supercells to identify precursors to severe weather reports. A dataset of left-moving supercells associated with severe weather reports was created. These storms are processed with an automated analysis algorithm that identifies and quantifies the polarimetric signatures in each storm. A method for analysis of differences and trends in their dual-polarization signatures in the 30 minutes prior to a severe weather report is developed. Z_DR columns and arcs are used to infer changes in storm and updraft strength. Z_DR arcs show no statistically significant differences leading to a severe hail report. The increase in reflectivity magnitude over the 30-minute analysis period prior to a severe hail report is statistically significant. The key finding from this research is that Z_DR columns show a statistically significant decreasing trend in both depth and areal extent leading to a severe hail report, which may be operationally valuable.

Advisor: Matthew S. Van Den Broeke