A Comparative Analysis of Near-Storm Environments for Tornadic and Nontornadic Significant-Hail Supercells using the Warn-on-Forecast System (WoFS)

Abstract The National Severe Storm Laboratory’s Warn-on-Forecast System (WoFS) is an ensemble of convection-allowing simulations designed for short-term (0–6 h) forecasting of severe weather, with the goal of helping the community move from a warn-on-detection to a warn-on-forecast paradigm. Although broader environmental conditions for severe weather in WoFS have been examined, no previous work has assessed meso-beta-scale environmental features adjacent to supercells that WoFS is able to resolve. A total of 41 supercells associated with local storm reports of either tornadoes rated at least EF1 or nontornadic significant hail (>51 mm diameter) are studied using WoFS simulations. The meso-beta-scale environments of tornadic and nontornadic significant-hail supercells are compared and contrasted using composite fields of salient parameters centered on the associated storm reports, and also by using back trajectories starting in the storm inflow region near the updraft at the time of the report. Composites reveal that WoFS simulates a noticeable pocket of high 0–500-m storm-relative helicity (SRH) that is significantly stronger and larger for tornadic than for nontornadic significant-hail supercells. Back trajectories also reveal environmental properties approaching the tornadic storms, such as consistently low lifting condensation levels and values of 0–500-m SRH that begin favorably and steadily increase.