Correlation Between Differential Reflectivity and Anomalous Cloud-to-Ground Lightning in Mesoscale Convective Systems

Cloud-to-ground (CG) lightning is a dangerous severe weather threat to life and property that can pose a challenge for forecasters performing impact-based decision support services (IDSS) at outdoor events. A majority of the time, the larger concerns for outdoor IDSS events are heavy precipitation and strong winds, with lightning being another equally dangerous concern. Schultz (2023) found that for mesoscale convective systems (MCS) in the eastern half of the United States, lightning detected by the Geostationary Lightning Mapper (GLM) originated from an area of greater than 30 dbz reflectivity just over ninety four percent of the time. However, CG lightning can occur several miles away from the precipitating regions of storms (anomalous strikes) and pose a challenge to those providing IDSS services for outdoor events. A case study by Schultz et al. (2021) investigated several of these anomalous lightning strikes, seven of which were CG, in the trailing stratiform region of an MCS that occurred on August 20, 2019 near St. Louis. Streaks of high differential reflectivity (ZDR) in the mixed phase region of the trailing stratiform area of this MCS were correlated with the occurrence of anomalous strikes.

Using CG lightning, ZDR, and reflectivity data from 13 trailing stratiform (TS) MCS cases examined in Schultz (2023), this study will investigate if a correlation between anomalous strikes and areas of high ZDR in the mixed phase region of an MCS’s trailing stratiform area regularly exists for MCS’s in the eastern half of the United States. The MCS cases are from the months of May through August in 2020 through 2022, in states east of the Rocky Mountains. Lightning data from these MCSs will be gathered from the National Lightning Detection Network (NLDN), reflectivity data will be gathered from Multi-Radar Multi-Sensor System (MRMS) data, and ZDR data will come from the NEXRAD Level 2 Data of the nearest WSR-88D radar station. A summary of the findings and example case studies will be presented.