Documenting storm severity in the mid-atlantic region using lightning and radar information

Abstract

Storm severity in the mid-Atlantic region of the United States is examined using lightning, radar, and model-derived information. Automated Warning Decision Support System (WDSS) procedures are developed to create grids of lightning and radar parameters, cluster individual storm features, and data mine the lightning and radar attributes of 1252 severe and nonsevere storms. The study first examines the influence of serial correlation and uses autocorrelation functionsto document the persistence of lightning and radar parameters. Decorrelation times are found to vary by parameter, storm severity, and mathematical operator, but the great majority are between three and six lags, suggesting that consecutive 2-min storm samples (following a storm) are effectively independent after only 6-12 min. The study next describes the distribution of lightning jumps in severe and nonsevere storms, differences between various types of severe storms (e.g., severe wind only), and relationships between lightning and radar parameters. The 2s lightning jump algorithm (witha 10 flashes min21 activation threshold) yields 0.92 jumps h21 for nonsevere storms and 1.44 jumps h21 in severe storms. Applying a 10-mm maximum expected size of hail (MESH) threshold to the 2s lightning jump algorithm reduces the frequency of lightning jumps in nonsevere storms to 0.61 jumps h21. Although radarderived parameters are comparable between storms that produce severe wind plus hail and those that produce tornadoes, tornadic storms exhibit much greater intracloud (IC) and cloud-to-ground (CG) flash rates. Correlations furtherillustrate that lightning data provide complementarystorm-scale information to radarderived measures of storm intensity © 2013 American Meteorological Society.