The utility of total lightning trends in diagnosing single-cell thunderstorm severity: Examples from the central Appalachians region

Abstract

The performance of a total lightning jump algorithm for guiding severe thunderstorm warnings within a weakly sheared environment was investigated using data from the Earth Networks Total Lightning Network. Total lightning observations from two summers for a study domain within the central Appalachian Mountains region were clustered into likely thunderstorms using single-linkage clustering. The spatial and temporal characteristics of each flash cluster were evaluated and used to assign a "storm index" (SI) score to each cluster. Small, short-lived, slow-moving, circular clusters-consistent with single-cell thunderstorms were given large SI scores, and large, long-lived, fast-moving, linear clusters-inconsistent with the single-cell mode-received smaller SI scores. Statistical testing revealed that days with a simple majority of lightning-defined (LD) single-cell storms possessed significantly weaker 0-6-km wind shear than days with a majority of non-single-cell storms. After classifying 470 clusters as either LD single-cell or multicell/supercell, the 2s lightning jump algorithm was applied to the flashes associated with each cluster. Total lightning jumps identified by the algorithm were aligned with severe weather report data to evaluate the accuracy of the algorithm. Although probability of detection values for both categories compared well to previous studies, false alarm rates were significantly larger than previously documented. The algorithm performed unsatisfactorily among the LD single-cell and multicell/supercell storms studied, and its performance deteriorated further when applied to a subset of storms most clearly defined as single-cell. However, severe LD storms demonstrated greater flash rates, a promising characteristic for future lightning-based warning tools.