Lightning activity within a tornadic thunderstorm observed by the optical transient detector (OTD)

The first storm-scale, total lightning observations from space during torna dogenesis are presented. During the overpass of an Oklahoma supercell, just minutes prior to tornado touchdown on 17 April 1995, the NASA (National Ae ronautics and Space Administration) OTD (Optical Transient Detector) detect ed a total of 143 flashes during approximately 3 minutes of observation tim e. The estimated total hash rate ranges from 45 (raw counts) to 78 (correct ed for detection efficiency) flashes min(-1). This total flash rate was at least 17 times greater than the cloud-to-ground lightning rate detected by the National Lightning Detection Network (NLDN), indicating most of the lig htning was intracloud. Cloud-to-ground lightning at this time was also domi nated by positive polarity flashes. In addition, total lightning rates were decreasing rapidly prior to touchdown. These OTD observations are consiste nt with the limited results from recent ground based measurements of total lightning activity in tornadic storms and corroborate that such storms have unusually high total flash rates, are dominated by intracloud lightning, a nd that the total flash rates are observed to decrease rapidly in the minut es prior to touchdown.