Re-examining the Relationship Between Polarity of Cloud-to-Ground Lightning Flash and Storm Severity

Linkages between storms with enhanced presence of positive Cloud-to-Ground (+CG) polarity lighting flashes and severe weather are well established. In contrast, this study identifies and tracks hundreds of weakly convective +CG dominant storms over the U.S. The tracking is based on the Warning Decision Support System -- Integrated Information (WDSS-II, from Nexrad) and the CG lightning information is acquired from the National Lightning Detection Network.

The tracked storms are characterized for total CG flashes and respective polarity, total Vertical Integrated Liquid (total VIL), maximum VIL, maximum Expected Size of Hail (MESH), Reflectivity at -10°C, areal extent, duration (from WDSS-II) but also Convective Available Potential Energy (CAPE) and Convective inhibition (CIN) from reanalysis. Each of the identified +CG dominant storms is further compared to -CG dominant storms that bear similar (±10%) characteristics in terms of total CG, duration and size. This is done to avoid the comparison between storms of disparate dynamic environments (e.g. Mesoscale Convective System vs. single cell)

The statistical comparison between dominant +CG vs. dominant -CG storms strongly advocates that the total VIL normalized by the storm’s areal extent is by far a better proxy to distinguish between the two storm categories, than the other implemented variables.