Comparing Polarimetric Signatures of Proximate Pretornadic and Non-Tornadic Supercells in Similar Environments

Abstract

While prior research has shown that characteristics of the supercell environment can indicate the likelihood of tornadogenesis, it is common for tornadic and non-tornadic supercells to coexist in seemingly similar environments. Thus, some small-scale factors must support tornadogenesis in some supercells and not in others. In this study we examined polarimetric radar signatures of proximate pretornadic and non-tornadic supercells in seemingly similar environments to determine if these radar signatures can indicate which proximate supercells are pretornadic and which are non-tornadic. We gathered a collection of proximity supercell groups and developed a method to quantify environmental similarity between storms. Using this method, we selected pretornadic – non-tornadic supercell pairs in close proximity in space and time having the most similar environments. These pairs were run through an automated tracking algorithm which quantifies polarimetric signatures in each supercell. Supercells with larger differential reflectivity (ZDR) column areas were more likely to become tornadic within the next 30 minutes compared to neighboring supercells with smaller ZDR column areas. In about two-thirds of pairs, the pretornadic supercell had a larger ZDR column area than the non-tornadic supercell prior to its maximum low-level rotation, which is consistent with much prior work. ZDR arcs could not discriminate between pretornadic and non-tornadic supercells, and hailfall area was larger in pretornadic supercells. The separation distance between the specific differential phase (KDP) foot and the ZDR arc was larger in pretornadic supercells yet was a limited result due to the small sample size used for comparison.