Total lightning observations of severe convection over North Texas

Abstract

Five severe convective cells over North Texas from three separate dates were examined to determine what three dimensional, or “total” lightning data can add to the understanding of a convective cell’s intensity, propagation, and severe weather potential. Total lightning data were obtained from Vaisala Inc.’s Dallas/Fort Worth (D/FW) Lightning Detection and Ranging (LDAR) network. Radar data from two Weather Surveillance Radar – 1988 Doppler (WSR-88D) sites were used for position data and information regarding the intensity and kinematic properties of each cell. Total lightning products used by the National Weather Service Forecast Office in Fort Worth, Texas were compared to total lightning flash rate; a quantity that has been shown to be correlated to changes in cell intensity inferred from other sources, such as radar and satellite data. These products, specifically flash extent density (FED) were also compared to CG flash rate and radar derived measures from the WSR-88D sites. The results of this work show that FED and total flash rate are well correlated, with an average Pearson correlation value of 0.73, indicating that previous total flash rate results may also apply to FED. Lightning hooks, holes, and notches in FED displays indicated likely updraft regions, while appendages were observed to develop prior to deviant motion with two supercells. These results, combined with a greater update frequency provided a useful complement to radar data in the warning decision process. FED jumps were observed prior to several severe weather reports, indicating that total lightning activity may be related to updraft strength as found in past studies. However, FED jumps were sometimes observed without any associated severe event. More work is clearly needed to define what FED changes are of most importance in the short-term prediction of storm severity. The usefulness of the total lightning data on these dates was dependant upon LDAR network status and distance of the cell from the network center. The results of this study suggest that combining total flash rate trends with visual displays of FED provides the greatest added benefit to forecasters in maintaining situational awareness during warning operations.