The Utility of Incorporating ZDR and KDP Signatures into the Tornado Warning Process: ZDR/KDP Separation and ZDR Arc Considerations in Supercells

Prior research has investigated the potential usefulness of interrogating certain dual-polarization radar fields in tornadic situations. The two primary variables of focus were differential reflectivity (Z_DR) and specific differential phase (K_DP).  It was shown that in tornadic events, areas of enhanced Z_DR typically resembled an arc-shaped configuration.  These Z_DR arcs tended to form along the right inflow sides of the parent supercells, indicative of areas of preferentially large raindrops near the leading edge of the forward flank.  In the meantime, regions of enhanced K_DP and lower Z_DR tended to develop much deeper into the storm, indicative of high liquid water content areas and the inclusion of smaller raindrops. 

Building upon the above outlined results, this research investigated significant severe weather events, where both tornadic and non-tornadic supercells were featured.  While previous dual-polarization studies were conducted in specific geographical regions of the United States, this study has looked at a number of cases that occurred east of the Rocky Mountains, in an effort to find a unified, geographically independent approach on using dual-polarization radar fields in the tornado warning decision-making process.  The most important, specific features of note were the separation characteristics between Z_DR and K_DP maxima in the forward flank, as well as the behavior of the Z_DRarc.  The implications of these signals with regards to drop size diameter distributions in certain supercell sectors, low-level storm-relative flow, storm-scale shear, and tornadogenesis potential will be discussed.  We will also briefly introduce future plans to investigate separate dual-polarization signatures in the hook echo regions of supercells.   

While the initial results look extremely promising, it is hoped these findings stimulate additional research to further improve our ability to differentiate between storms that produce tornadoes, from those that do not.