The use of passive radar for mapping lightning channels in a thunderstorm

The state of Georgia has experienced a number of tornadoes that occur without warning and in several cases have caused fatalities. Researchers at the Severe Storms Research Center (SSRC) of the Georgia Tech Research Institute (GTRI), Georgia Institute of Technology are attempting to detect tornado formation within severe thunderstorms occurring in the vicinity of Atlanta, Georgia using non-radar sensors that may provide early tornado warning and provide cueing to existing national weather service (NWS) radars. The goal of these studies is to increase the warning time of tornado formation within the parent thunderstorm. GTRI researchers use real time S-band Doppler weather radar data from three national weather service (NWS) WSR-88D NEXRAD radars to complement the development of the non-radar tornado sensors. Three NWS Doppler radars provide severe weather surveillance coverage of the north Georgia area to determine if a thunderstorm contains the Doppler signature that indicates tornado formation. The radar data, displayed on a work station developed and optimized for tornado detection by the National Severe Storms Laboratory (NSSL), serves as ground truth data for the non-radar sensor development. GTRI can display cloud to ground (CG) lightning strikes, a capability provided by overlaying data from a national monitoring network onto the radar reflectivity map. GTRI also uses a local lightning direction finder (DF) system that supplies azimuth and range to the lightning strike. This paper discusses the early lightning channel research and the passive parasitic radar system being operated by the SSRC.