Life Cycle and Precipitation Formation in a Hybrid-Type Hailstorm Revealed by Polarimetric and Doppler Radar Measurements

Abstract

Hailstorm processes are studied using multiparameter radar observations of thunderstorm evolution. The storm turned out to be of hybrid type, having both multicellular (oscillatory nature of hail production) and supercellular (quasi-steady state of basic dynamics) characteristics. Its reflectivity field showed a V-like pattern not yet described in the literature as a typical severe storm pattern. The flow was characterized by an updraft zone surrounding an embedded downdraft collocated with the main precipitation shaft. The precipitation mainly originated from graupel particles growing at the fringes of the main updraft zone, whereas an accumulation zone of big drops was not present. In the weaker parts of the updraft the falling graupel melted and reached the ground as rain, whereas in the main updraft region those raindrops could be recirculated and subsequently freeze or be captured by hailstones already present aloft. In this region of high liquid water content large hail could be grown; it fell out in the main downdraft region immediately beside the main updraft zone. Comparison of the radar-derived hailswath and ground observations of hail damage gave encouraging verification of the LDR-ZDR hail signature defined in this paper.