A Statistical Study of the Association of DRCs with Supercells and Tornadoes

Abstract

A new three-dimensional reflectivity echo in the rear flank of supercells known as the descending reflectivity core (DRC) has been documented in the literature by Rasmussen et al. The DRC is an enhanced region of reflectivity presumed to occur in the rear-flank downdraft (RFD) of a supercell. In the four cases they studied, this feature descended with time from the rear-echo overhang at 3?6 km in height into the supercell appendage. In addition, the DRC often occurred prior to tornadogenesis. The purpose of this paper is to serve as a more thorough analysis of DRCs using a larger sample of storms. The frequency of DRCs is explored within isolated supercells with persistent rear-flank appendages, and in particular at times preceding reported tornado onset in those supercells. Of the 64 supercells included within this study, 59% produced DRCs, with 30% of these DRCs occurring within 10 min prior to 5 min after tornadogenesis. This study included 89 reported tornadoes and 71 DRCs. Statistical analysis of the dataset reveals that while DRCs are sometimes associated with tornadoes, they presently have limited usefulness for tornado nowcasting. Improvements to Weather Surveillance Radar-1988 Doppler (WSR-88D) resolution and further classification of DRCs may help discriminate between tornadic and nontornadic appendages in the future, however.