Lightning Characteristics and Relationship to Preliminary Local Storm Reports

The Storm Prediction Center (SPC) has traditionally utilized cloud-to-ground (CG) lightning for a variety of purposes but recently intra-cloud (IC) flash data as part of total (CG + IC) lightning has been made available. To further explore characteristics of considering both CG and IC flashes in an operational setting, a systematic evaluation and comparison of the Vaiasala’s National Lightning Detection Network (NLDN) and Earth Networks Total Lightning Network (ENTLN) data sets for all of 2014 was performed to provide some initial statistical characteristics. In addition, the relationship of lightning flashes to preliminary severe and winter-weather Local Storm Reports (LSRs) was explored on an hourly, high-resolution grid covering the contiguous United States. Results showed that thunderstorms became more numerous in April with a marked increase in IC lightning flashes during the summer compared to the steadier rise of CG activity. Aggregate annual counts from the ENTLN and NLDN show similar CG flash patterns, but NLDN CG detections were 1.22 times more numerous than ENTLN detections. Furthermore, tallies of IC flashes were often more extensive and numerous than CG flashes across the contiguous United States and ultimately contributed a substantial portion [~0.89] to total lightning. On a national scale, hourly cumulative CG (total) lightning flashes reached their greatest count for the year at 2200 UTC (2300 UTC) with the lowest sum for the hour ending at 1600 UTC (1500 UTC). Not surprisingly, locations in Florida and along the Gulf Coast exhibited the highest frequency of thunderstorms with a secondary max more evident with the IC flash dataset in the Missouri Valley. Finally, the time/space matching of LSRs and lightning was accomplished through a direct grid-point to grid-point comparison and application of a spatial neighborhood approach, with the latter exhibiting a higher number of matches. More precisely, severe (winter) weather type LSRs consistently (rarely) coincided with lightning, as greater (less) than 97% (1%) of grid-points met the matching criteria. The greatest concentration of severe LSRs without lightning occurred near the Mid-Atlantic States. On the other hand, principal locations for winter LSRs with lightning stretched from the Central and Southern Plains northeastward towards the Great Lakes, with a secondary maximum over the Rocky Mountains.