Linking satellite based lightning initiation nowcasts with WRF lightning threat forecasts to produce a combined nowcast of lightning onset and extent

Nowcasting 0-1 hour lightning initiation (LI) from geostationary satellite data is a recently developed concept with plans for integration into a mature convective initiation algorithm, the SATellite Convection AnalySis and Tracking (SATCAST) system. Harris et al. (2010) used SATCAST to quantify the behavior of ten Geostationary Operational Environment Satellite (GOES-12) infrared interest fields beginning 1-hour in advance of LI. Results indicated that an average lead time of 35 minutes prior to LI can be made using SATCAST, with a range from 15 minutes to 1 hour. Work is currently being done to implement this into realtime satellite-based systems.

The Weather Research and Forecasting (WRF) model currently outputs lightning threat forecasts developed by McCaul et al. (2009). These 2-km resolution forecasts are based on proxy fields of graupel flux at -15° C and vertically integrated ice. These forecasts offer a time and spatial coverage of lightning threat density. Currently, work is underway to investigate the benefits of combining the WRF model lightning threat output with the SATCAST system. Data are being collected from the North Alabama Lightning Mapping Array (NALMA) to provide a ground truth of lighting density. WRF model output from the corresponding days is being analyzed to find a correlation between the lightning threat product and actual lightning observed, both in extent of lightning, as well as location. Data from SATCAST interest fields are also being collected for comparison with the flash density results. The goal is to develop an algorithm that will provide a nowcast of LI along with the potential flash density associated with the future convection.