Airflow and hail growth in a severe Northern High Plains supercell

Abstract

Air and particle trajectory calculations using internal motions from Doppler radar observations are used to identify kinematic features and hail growth processes operating in a supercell storm. It produced a significant hailfall composed mostly of 2 to 3 cm diameter hailstones. Some diameters were as large as 6 to 10 cm. At least one funnel cloud was sighted, and there was extensive crop and property damage. In the hail growth model 1 to 5 cm hailstones were readily produced from frozen drops in the size range 50 μm to about 1 mm. Most of the hail apparently grew from frozen droplets that originated within either the upward stagnation zone southwest of the main updraft core or the overhanging radar echo ahead of the updraft. Potential hailstone embryos entered the stagnation zone from a flanking cloud line associated with the surface gust front. Graupel particles grown in this weak updraft region were carried by the southwesterly airstream either into the hook echo or into the forward overhang. Hail from this large, severe supercell was produced along several paths, some similar to prajectories proposed for other storms and some different. Overall, the hail growth is more complicated in this well-documented storm than in any of the simple idealizations previously proposed. -from Authors