Localizing tornado climatology in the contiguous United States: An environmental parameter and convective mode focus

The objective of this study is to document the spatial distribution of environmental parameters and convective mode associated with tornadic storms across the contiguous United States during 2003-2011. The tornado events were comprised of tornado segment data and filtered by the maximum event magnitude per hour on a 40-km Rapid Update Cycle model horizontal grid. Environmental information accompanied each grid-hour event from the hourly objective analyses calculated and archived at the Storm Prediction Center (SPC). Analysis of tornado distribution by convective mode and environmental parameters was accomplished through the creation of histograms by radar site and spatial maps over the contiguous United States. Results revealed regional variation amongst different parameters [e.g., 0-1 km storm relative helicity (SRH), lowest 100-mb mean-layer lifted condensation level height (MLLCL)] associated with right-moving tornadic supercells. MLLCL for tornadic environments demonstrated a notable shift from lower values in the southeastern United States to higher values farther north and west. The opposite distribution was noted in 0-1 km SRH, with higher values in the southeastern United States than across the Great Plains. This tendency was further investigated to determine if a difference could be noted between weak (EF0-EF1) and strong (EF2+) tornado events with a focus on the southeastern United States. Finally, the effects of buoyancy on events with a high 0-1 km SRH were analyzed.