Radar Detection of Tornadogenesis

Determining whether a given supercell will go on to produce a tornado has been a task that has proven to be very difficult. While features like the tornado vortex signature (TVS) or tornado debris signature (TDS) have been found to aid in determining whether a supercell has sufficient rotation to form a tornado or if a tornado is ongoing, there are no known features that are reliable indicators of tornadogenesis or a lack thereof. This study compares tornadic and non-tornadic supercells in an attempt to find such features using polarimetric Level-II radar data from Weather Surveillance Radar-1988 Doppler (WSR-88D) in Iowa, Missouri, Nebraska, and Kansas. The set of non-tornadic supercells is determined by looking for “radar indicated rotation” in a tornado warned storm, then using a pseudovorticity calculation to ensure that the supercell would otherwise be capable of producing a tornado. A visual analysis of base reflectivity (BR), spectrum width (SW), differential reflectivity (Z_DR), correlation coefficient (ρ_hv), and specific differential phase (K_DP) is then performed looking for features that either appear only prior to tornadogenesis in the tornadic supercells and not in the non-tornadic supercells or appear only in the non-tornadic supercells and not in the tornadic supercells. It is expected that features will be found. Statistical analysis will then be performed on these features to determine how reliable they are.