Comparisons of observer reports of thunderstorms with similar reports derived from the National Lightning Detection Network Data

An analysis was performed of the comparison between manually observed thunderstorm observations and the observations to be reported by automated observing systems using the Automated Lightning Detection and Reporting System (ALDARS) algorithms and lightning flash data from the National Lightning Detection Network (NLDN). Thunderstorm minutes, reported by observers at a sample set of airports, were consistent with NLDN-based reports that used lightning flashes occurring within 10 and 30 N.M of these same airports. The results of this analysis were very similar to those of an earlier study that helped validate the application. An important additional insight was obtained from the present and previous (1995 analysis) results. It was found that, irrespective of differences in null observational periods during thunderstorms detected by both observers and the NLDN, the intersection of thunderstorm minutes reported by observers with the NLDN-based variation of thunderstorm minutes with range from the airport location of interest occurs at a distance of approximately 13 N.M. This result is consistent with previous studies on the human's ability to hear thunder. It further suggests that this distance may be taken as representative of the maximum threshold distance out to which human observers are able to perceive the occurrence of thunder.