Lightning initiation forecasting: an operational dual-polarimetric radar technique

The objective of this study is to develop and test operational forecast algorithms for the prediction of lightning initiation utilizing the C-band dual-polarimetric radar, UAHuntsville's Advanced Radar for Meteorological and Operational Research (ARMOR). Although there is a rich research history of traditional radar signatures associated with lightning initiation, few studies have utilized dual-polarimetric radar signatures and capabilities, e.g. differential reflectivity columns and fuzzy-logic Particle IDentification (PID) of precipitation ice, respectively. The scientific goal of this study is to develop and test polarimetric techniques that enhance the performance of current operational radar reflectivity based first flash algorithms. The operational goal is to improve lightning watch and warning performance for operational uses at locations such as NASA Kennedy Space Center, Cape Canaveral Air Force Station, and National Weather Service stations to enhance personnel safety and reduce costs from false alarms. In addition, these techniques may also help improve personnel safety and costs in other industries, such as airfield management in commercial aviation and outdoor entertainment and recreation with additional improvements of safety in private recreation. The hypothesis is that the additional dual-polarimetric information could potentially reduce false alarms while maintaining high probability of detection and increasing lead-time for the prediction of the first lightning flash relative to reflectivity-only based techniques. To test the hypothesis, various physically-based techniques using polarimetric variables and/or PID categories, which are strongly correlated to initial storm electrification (e.g., large precipitation ice production via drop freezing), were benchmarked against the operational reflectivity-only based approaches to find the best compromise between forecast skill and lead-time. Through the analysis of eight case dates, consisting of 35 pulse-type thunderstorms and 20 non-thunderstorm case studies, lightning initiation forecast techniques were tested. Forecast performance is determined by statistical analysis of probability of detection (POD), probability of false alarm (PFA), critical success index (CSI), lead-time, and other performance metrics such as the Operational Utility Index (OUI) developed by 45th Weather Squadron specifically for lightning warnings. This study is funded by NASA Marshal Spaceflight Center and NOAA Collaborative Science, Technology, and Applied Research Program.