C-band Dual-Polarimetric Observations of Snowfall in a Southeastern Thundersnow Event

A unique study of a rare heavy winter snow event in the Southern US is examined. This event was observed with high quality dual polarimetric radar data from the Advanced Radar for Meteorological and Operational Research (ARMOR) C-band dual polarimetric radar and the three-dimensional VHF lightning mapping array (LMA) located in Huntsville, AL. Seven lightning flashes were observed by the LMA during a period of intense snowfall in North Central AL. Observed snowfall rates during the period of electrical activity were on the order of 5-8 cm per hour. Idealized T-matrix simulations of ice crystal radar parameters at C-band were accomplished in order to better understand the ARMOR observations in heavy snow. The combination of ARMOR dual polarimetric radar and VHF LMA observations suggested contiguous layer changes in height between sloping aggregate-dominated layers and horizontally-oriented crystals. These layers may have provided ideal conditions for the development of extensive regions of charge and resultant horizontal propagation of the lightning flashes over large distances. Interestingly, at least 4 of 7 lightning flashes examined in this event appeared to initiate from communications towers before propagating upward into well defined layers in the clouds.