Demonstrating the Utility of Conditional Probabilities of Tornado Damage Rating in the Impact-Based Warning Era

The Storm Prediction Center developed conditional probabilities of tornado damage rating from near-storm environment data and radar-based storm-scale characteristics from a 5-year sample of tornadoes (>4,700) reported in the contiguous United States (CONUS) during 2009-2013. The probabilities are derived from filtering tornado segment data by the maximum EF-scale tornado event per hour on a 40-km horizontal grid. Near-storm environment data, consisting primarily of supercell-related convective parameters from hourly objective mesoscale analysis calculated at the Storm Prediction Center (SPC), accompanied each tornado grid-hour event. Convective mode was assigned to each tornado event by manually examining full volumetric WSR-88D data at the beginning time of each event. Peak 0.5° rotational velocity was also manually identified immediately prior to and during the duration of each tornado event.

A best-practices approach for short-term tornado hazard diagnosis considers the use of information from 1) near-storm environment, 2) convective mode, 3) peak 0.5° rotational velocity and 4) supporting or confirming evidence of a tornado as a unifying frame-of-reference. A few examples highlighting the strengths and weaknesses of applying this conditional probability technique will be discussed.