A Preliminary Polarimetric Radar Comparison of Pretornadic and Nontornadic Supercell Storms

Abstract

Supercell thunderstorms produce a variety of hazards, including tornadoes. A supercell will often exist for some time prior to producing a tornado, while other supercells never become tornadic. In this study, a series of hypotheses is tested regarding the ability of S-band polarimetric radar fields to distinguish pretornadic from nontornadic supercell storms. Several quantified polarimetric radar metrics are examined that are related to storm inflow, updraft, and hailfall characteristics in samples of 19–30 pretornadic and 18–31 nontornadic supercells. The results indicate that pretornadic supercells are characterized by smaller hail extent and echo appendages with larger mean drop size. Additionally, differential reflectivity ZDR column size is larger and less variable in the pretornadic storms in the 25–30 min prior to initial tornadogenesis. Many of the results indicate relatively small polarimetric differences that will likely be difficult to translate to operational use. Hail extent and ZDR column size, however, may exhibit operationally useful differences between pretornadic and nontornadic supercells.

Polarimetric Radar Characteristics of Tornadogenesis Failure in Supercell Thunderstorms

“…Over time, characteristic radar signatures in supercell storms have been quantified, e.g., [5][6][7]. Quantification facilitates comparison between subsets of storms and allows inferences about storm structural and microphysical changes through the supercell life cycle, including around the time of tornadogenesis and tornado demise, e.g., [8][9][10][11]. This study extends prior work by focusing on polarimetric radar signatures during pre-tornadogenesis failure (TGF) analysis periods in nontornadic supercell storms.…”

“…The work reported here is an extension of that presented by [11], who compared long temporal periods in nontornadic storms to shorter (30 min) pre-tornadic periods in tornadic storms. In that work, the primary findings most important for future work included (1) smaller extent of radar-inferred hailfall at low levels in pre-tornadic supercells.…”

“…In this work, radar signatures are examined for the first time within equal-length periods prior to tornadogenesis and TGF in a sample of supercell storms. This builds on the work of [11] by only considering nontornadic storms that experienced TGF and by comparing equal-length analysis periods before tornadogenesis and TGF, allowing direct comparison between these two storm subsets. Given the findings of prior studies we here hypothesize that pre-TGF periods will contain weaker and less-steady midlevel updrafts than pre-tornadic periods, will contain larger areas dominated by hail, and will be characterized by larger storm-core Z HH values on average.…”

Disdrometer, Polarimetric Radar, and Condensation Nuclei Observations of Supercell and Multicell Storms on 11 June 2018 in Eastern Nebraska

“…Z DR data from the WSR-88D were calibrated following the procedure of [29], which is also applied by [17,30]. From the radar dataset, the low-level scan nearest the midpoint of the disdrometer dataset was selected (~2206 UTC) and all pixels~1.5 km above the ambient 0 • C level in convective anvil regions with 20 dBZ ≤ Z HH ≤ 35 dBZ were selected.…”

“…Atmosphere 2020, 11, x FOR PEER REVIEW 4 of 18 ZDR data from the WSR-88D were calibrated following the procedure of [29], which is also applied by [17,30]. From the radar dataset, the low-level scan nearest the midpoint of the disdrometer…”