An Intercomparison Between Observational and High-Resolution Model Data of Dual-Polarization Radar Signatures in Tornadic and Nontornadic Supercells During the 24 – 25 May 2011 Outbreak

Supercells tend to produce the strongest and longest-lived tornadoes, causing significant destruction of property, loss of life, and impacts to society. To mitigate these impacts, understanding the formation of supercell tornadoes is crucial. There are many studies that assess the predictability of tornado formation and failure across various environments. Within this subset of studies, there is both observational and simulation work that relates dual-polarization radar signatures with tornado formation and intensity. However, such studies have yet to address how both tornado failure and genesis occur within the same environment, and if this distinction is predictable using dual-polarization radar signatures. With this in mind, this study examines dual-polarization radar signatures across supercells that occurred during the 24–25 May 2011 tornado outbreak using both the KOUN NEXRAD radar and from a simulated ensemble of supercells in the same environment. The 24–25 May 2011 KOUN dataset provides a suite of full lifecycle observations of storms that produced strong, long-lived tornadoes; weaker, shorter-lived tornadoes; and storms that produced no tornado at all. There are three ensembles of CM1 simulations that accompany the NEXRAD observations, each using a different microphysics scheme: the Morrison 2-moment, NSSL 2-moment, and NSSL 3-moment scheme. Small variations in the microphysical parameters are used to introduce intrinsic predictability into each model ensemble. Not only can these simulations be compared to the NEXRAD observations, but they provide the unique opportunity to assess the impacts model microphysics schemes have on the simulated evolution of dual-polarization supercell signatures. The following dual-polarization radar signatures for each supercell were analyzed at each time step: differential reflectivity (Z_DR) column area and height, Z_DR arc area and centroid, and specific differential phase (K_DP) foot area and centroid. Preliminary analyses from the observed data show that, while the Z_DR column heights across the suite of supercells are similar, supercells that produced the strongest tornadoes have larger Z_DR column areas than the nontornadic supercell. Furthermore, there is only a clear distinction in Z_DR arc and K_DP foot area between the strongest tornado in the ensemble and the rest of the ensemble members. However, the temporal evolution shows increases in Z_DR arc area within 30 minutes of tornadogenesis for most ensemble members and increases in K_DP foot area within 30 minutes of tornadogenesis for all ensemble members. Future results will highlight comparisons of the same dual-polarization features across the three CM1 ensembles and NEXRAD observations. The comparison of dual-polarization radar signatures in supercells in the same environment is directly applicable to forecasting as potential distinctions in dual-polarization radar signatures across nontornadic, weakly tornadic, and strongly tornadic supercells can lead to longer lead times for warnings in addition to providing extra forecast information for operational meteorologists.