ZDR Column Behavior in Real and Simulated X-band Radar Observations of Potentially Tornadic Storms

Jaime Louise Herriott, Robin L Tanamachi

The primary objective of this research is to characterize distinct differential reflectivity (ZDR) column behavior with respect to height, intensity, and aerial coverage prior to tornadogenesis (failure) in X-band radar observations of supercells. ZDR observations of three supercells observed at high spatiotemporal resolution with X-band polarimetric radar, two tornadic and one nontornadic, are examined. Similar ZDR column behavior is found in all three, despite divergent outcomes with respect to tornadogenesis. ZDR columns are also generated from a 30-member ensemble of simulated supercells.  Height, intensity and areal extent of the simulated ZDR columns are investigated just above the 0°C level. Simulated ZDR column area and height both increase and ZDR intensity inside the column was higher, on average, in the 5 min prior to tornadogenesis, whereas there was no appreciable change in these metrics for tornadogenesis failure. This result stands in contrast to results from our observational analysis, where there were no consistent, distinguishable changes in ZDR column metrics prior to tornadogenesis versus failure. This research pinpoints ZDR column metrics that can be the focus of future study, both through field observations and numerical simulations.