The discrimination between tornadic and nontornadic supercell environments: A forecasting challenge in the southern United States

Recent results from storm-scale modeling experiments have suggested that the strength of the 3-7-km storm-relative wind plays a very important role in determining whether or not a storm that already exhibits midlevel updraft rotation will, in fact, develop a persistent low-level mesocyclone, a feature commonly observed prior to tornadogenesis. This concept and others are applied to a total of 73 southern U.S. proximity soundings that have been compiled over a 36-yr period, 1960-95, in an attempt to discriminate between tornadic and nontornadic supercell environments. Of the 73 proximity soundings, 45 were classified as southern plains tornadic and 28 were southern plains nontornadic. The results of this study suggest that strength of the 2-9-km storm-relative wind, when used in combination with some measure of thermodynamic instability, or even the energy-helicity index, has proven to be a good indicator of whether or not an environment is supportive of tornadic supercells. Also, the magnitude of the 0-6-km wind shear was observed to be significantly higher in the tornadic soundings in comparison to the nontornadic cases.