Analysis of Lightning Trends Prior to the Occurrence of Severe Weather Events

An evaluation of lightning trends prior to the occurrence of severe weather in the contiguous United States (2011-12) was performed using lightning cell tracking data from the Earth Networks Total Lightning Network (ENTLN) and National Weather Service Local Storm Reports (LSRs). Consistent one minute total lightning (in-cloud (IC) and cloud-to-ground (CG)) data are compiled thirty minutes before and after an LSR for lightning cells existing within 10, 20, and 40 km radii of a severe weather event. Many individual cases exhibit a total lightning “jump” prior to severe weather with a subsequent “drop” in lightning activity by the time of occurrence. Overall, median total lightning peaks during the 30 minutes leading up to tornado, hail, and high wind events. An approximate 15% decrease in total lightning from peak to time of event occurrence provides sample wide evidence of the “jump” and “drop” trend. Moreover, statistical evidence exists to support the observation of 15-20% higher total lightning rates within +/- 30 minutes of tornado events as compared to hail and high wind events. Using a modified version of the lightning jump detection algorithm proposed by Gatlin et al. (2010), jump detection using a 2σ approach is compared to utilizing a simple threshold approach for predicting severe weather.