22 Verification of RUC Analyses using VORTEX2 Soundings for Nontornadic and Tornadic Supercell Environments

Monday, 7 November 2016
Broadway Rooms (Hilton Portland )
Brice E. Coffer, North Carolina State University, Raleigh, NC

Handout (989.3 kB)

In the past two decades, considerable progress has been made regarding our understanding of how lower tropospheric profiles of temperature, humidity, and winds favor nontornadic versus tornadic supercells. These advancements have primarily been based on proximity soundings derived from the RUC model, due to insufficient coverage of observed upper-air radiosondes. However, NWP models inherently rely on parameterization schemes to account for process not represented on the grid-scale, and this can lead to errors in both the analyses and forecasts when compared to observed soundings (even at 0 and 1 hr). Issues in the planetary boundary layer are of particular interest in the present work because of the importance of boundary layer humidity and near-surface storm-relative helicity in the supercellular tornadogenesis process. In observed proximity soundings, previous studies have shown that storm-relative helicity in the lowest 500 m demonstrates the highest discrimination between nontornadic and tornadic supercells. In fact, the low-level wind orientation and 0 - 500 storm-relative helicity were the most striking environmental difference between the VORTEX2 nontornadic and tornadic supercells. In this study, the observed VORTEX2 near-inflow soundings will be compared to the corresponding RUC 00 hr analyses in an attempt to answer the question of whether our best-available gridded observation dataset can reproduce the seemingly subtle differences between the environments of non-tornadic and tornadic supercells surveyed during VORTEX2.
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