Radar Nowcasting of Total Lightning over the Kennedy Space Center

Abstract

long-term radar dataset over Melbourne, Florida, was matched with three-dimensional lightning data to optimize radar-derived predictors of total lightning over the Kennedy Space Center (KSC). Four years (2006?09) of summer (June?August) daytime (about 1400?0000 UTC) Weather Surveillance Radar-1988 Doppler data were analyzed. Convective cells were tracked using a modified version of the Storm Cell Identification and Tracking (SCIT) algorithm, and correlated to cloud-to-ground (CG) lightning data from the National Lightning Detection Network (NLDN) and grouped intracloud (IC) flash data from the KSC Lightning Detection and Ranging (LDAR) I and II networks. Reflectivity values at isothermal levels and a vertically integrated ice (VII) product were used to optimize radar-based forecasting of both IC and CG lightning. Results indicate the best reflectivity threshold predictors of CG and IC lightning according to the critical success index (CSI) were 25 dBZ at ?20°C and 25 dBZ at ?15°C, respectively. The best VII predictors of CG and IC were the 30th (0.840 kg m?2) and 5th percentiles (0.143 kg m?2), respectively, suggesting less ice mass is needed in the main mixed-phase region for IC flashes to occur. In addition, VII at lightning initiation (both CG and IC) was higher than at cessation. Seventy-six percent of cells had IC initiation before CG initiation. Using the first IC flash as a predictor of CG occurrence also statistically outperformed other CG predictors, but yielded a 2.4-min average lead time. However, this lead time is comparable to the reflectivity threshold and VII methods when accounting for radar scan and processing time.