Abstract

This paper is motivated by the recent interest in the ‘‘descending reflectivity cores’ ’ (DRCs) that have been observed in some supercell thunderstorms prior to the development or intensification of low-level rotation. The DRCs of interest descend on the right rear flank of the storms and are small in scale, relative to the main radar echo. They are observed to descend from the echo overhang and, upon reaching low levels, have been found to contribute to the formation or evolution of hook echoes, which are perhaps the most familiar radar characteristic of supercells. Herein, observations of DRCs obtained by a mobile Dopp-ler radar at close range are presented. The data afford higher-resolution views of DRCs and their accom-panying radial velocity fields than typically are available from operational radars, although one drawback is that some of the larger-scale perspective is sacrificed (e.g., the origin of the DRC and its possible connection to the reflectivity near the updraft summit are within the cone of silence). It is found that it is difficult to generalize a relationship between the observations of DRCs and the subsequent evolution of the low-level wind field. The results of a three-dimensional numerical simulation of a supercell thunderstorm also are presented. DRCs are a common development within the simulation despite the use of a simple (warm rain) micro-