Diagnosing Total Lightning Potential with Differential Reflectivity Anomalies

Polarimetric radar data can characterize different hydrometeor types and sizes within a thunderstorm with various kinematic processes affecting fall speed and trajectory. Strong air currents, such as an updraft, can size sort raindrops with larger drops falling to the Earth and smaller drops lofted upward into the atmosphere. This deficit of small drops closer to the ground, where WSR-88D spatiotemporal resolution is optimal, produces a high differential reflectivity (Z_DR) footprint collocated with low values of reflectivity at horizontal polarization (Z_H). The local variance of Z_H/Z_DR reveals locations of ongoing updraft development with higher standard deviations potentially corresponding to stronger and long-lived updrafts. The occurrence and propensity of total lightning is known to be correlated with the updraft size and strength, yet, distinguishing which storms have the potential to produce prolific lightning in real-time has been a challenge in the weather forecasting and hazard mitigation communities.

Focusing initially on days with isolated convection, polarimetric Weather Service Radar 88 Doppler and Rapid Refresh analysis data were ingested into the Warning Decision Support System - Integrated Information environment to generate Z_H/Z_DR relationships and write out a field of standardized anomaly values. These values were compared to total lightning flash rates and density from Earth Network’s lightning network, the GOES-16 Geostationary Lightning Mapper, and research Lightning Mapping Arrays when available to determine the extent standardized differential reflectivity anomalies at various heights above the ground translates to first and total lightning frequency.