A study of lightning flashes attending periods of banded heavy snowfall

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Lighting[sic] flashes associated with 24 banded thundersnow events were analyzed to document their polarity, signal strength, and multiplicity. Radar reflectivity values were recorded at each lighting flash, as well as the maximum radar reflectivity within the associated snow band. The preferred location of the lightning activity within the snow band was also noted as being either leading edge (LE), trailing edge (TE), core (C), or not correlated (NC). Vertical profiles of radar reflectivity at the location of each lightning flash were generated using the Warning Decision Support System (WDSS), looking for pronounced convective signatures. Reflectivity values at each height were recorded and used to construct a composite vertical profile of winter convection near each flash. Additionally, the height of the -10 [degree sign]C isotherm for each of these lightning flashes was obtained from skew-T log-p analysis. This level is considered critical for charging processes in winter clouds, and its height has been shown to have a strong influence over the generation of winter lightning. The radar reflectivity at the height of the -10 [degree sign]C level was taken from the WDSS analysis to determine the average radar reflectivity at the height of the -10 [degree sign]C isotherm. In the central United States, a preference for negatively charged lighting was found for winter convection, which stands in contrast to the majority of the research done on winter convection in Japan. Single and multi-banded structures were observed to be a dominant feature of thundersnow events. The most pronounced location for a lighting discharge was found to occur in the core section of the band, while the majority of lightning activity was found on the leading edge of the highest areas of radar reflectivity within the snow bands. The average height of the -10 [degree sign]C isotherm was found to be 3872 m above ground level (AGL), with a corresponding radar reflectivity of ~ 22 dBZ. Although neither slantwise nor upright precipitation were the dominant type of precipitation systems found in thundersnow cases, the radar reflectivity within convective snow systems was found to be higher than typical winter-time snow storms.