Matthew Van Den Broeke
Date of this Version
Healey, Devon J.; Comparing Polarimetric Signatures of Proximate Tornadic and Non-Tornadic Supercells in Similar Environments, 2022; M.S. thesis, University of Nebraska-Lincoln Digital Commons.
While much research has shown that characteristics of the environment surrounding supercells can potentially indicate their likelihood to become tornadic, it is not uncommon for tornadic and non-tornadic supercells to coexist in seemingly similar environments. In these situations, it is difficult operationally to separate tornadic from non-tornadic supercells using environmental observations alone. Given that tornadic and non-tornadic supercells have been found to coexist in similar environments, something must be occurring beneath the observational and/or model gridscale that is supporting tornadogenesis in some supercells while inhibiting it in others. This study examines dual-polarimetric radar signatures of proximate tornadic and non-tornadic supercells in similar environments to determine if this can be a valuable method to distinguish proximate tornadic and non-tornadic supercells. Much research has examined dual-polarimetric signatures of supercells; however, not while controlling for environment between tornadic and non-tornadic supercells. A collection of proximity supercell groups is collected, and a method to quantify environmental similarity between storms is developed. Using this method, we select tornadic – non-tornadic supercell pairs that appear to have the most similar environment within proximity supercell groups. These pairs are run through an automated tracking algorithm which identifies and quantifies polarimetric signatures in each supercell. Differential reflectivity (ZDR) arcs show no statistically significant differences between supercells; however, the maximum value within the arc may be larger in non-tornadic supercells. The difference in separation distance between the ZDR arc and the specific differential phase (KDP) foot between tornadic and non-tornadic supercells is statistically significant, with tornadic supercells having larger separations. The key finding from this research is that tornadic supercells have larger ZDR column and hailfall areas in the 30 minutes prior to tornadogenesis. In about two-thirds of pairs, the tornadic supercell had a larger ZDR column area than the non-tornadic supercell prior to tornadogenesis. The statistically significant difference in ZDR column area between storms may be operationally beneficial.
Advisor: Matthew S. Van Den Broeke