Relationship of Low-Level Instability and Tornado Damage Rating Based on Observed Soundings

Upper-air soundings were collected for weak (EF-0/EF1), significant (EF2/EF3), and violent (EF4/EF5) tornadoes within the proximity (i.e., 100 km and 6 hours) of a sounding observation. A total of 50 proximity soundings for violent tornadoes, and random samples of 100 proximity soundings for significant tornadoes and 102 for weak tornadoes were analyzed after filtering and quality control. A variety of severe-weather parameters were compared among the tornado datasets. Low-level instability parameters (0-3 km lapse rates and 0-3 km mixed-layer convective available potential energy) were the best predictors of tornado strength (as estimated by damage rating), whereas lifted condensation level, wind shear, and effective storm relative helicity were not effective in discriminating between significant and violent tornado environments. While the significant tornado parameter (STP) was found to discriminate statistically between violent and significant tornadoes, a new parameter, the violent tornado parameter (VTP), is introduced and includes low-level instability parameters in order to better differentiate between significant and violent tornado environments.