Extended Abstract (520K)P2.8
The mechanics of falling hailstones and hailswaths
Kevin Vermeesch, Purdue University, West Lafayette, IN; and E. Agee
Supercell thunderstorms are known to be excellent producers of large, destructive hail. The strong updrafts within the thunderstorm can sustain large hailstones, many of which are spheroids, and some of which can become irregularly-shaped with knobs, lobes, or spikes on their surface. Such irregular surface characteristics can alter the drag coefficient of hailstones, causing them to fall faster if supercritical Reynolds number flow is achieved. It is one focus of this study to examine such hailstone fall conditions and determine their similarity to nature. Besides these special cases of hailstones, the descent of hail from a thunderstorm is also studied with respect to updrafts and downdrafts, thunderstorm translational speed, internal thunderstorm rotation, turbulence, and density variations of both the hail and the atmosphere. These factors determine the speed at which the hailstone strikes the ground, which in turn partly determines the amount of damage the hailstorm is capable of producing, along with the hailswath. In the second part of this study, given that the conditions of hail fall are known, the hailstone's landing location on the ground with respect to the center of mesoscale circulation will be calculated. In thunderstorms that exhibit rotation, they produce a size-sorted hailswath on the ground where larger hailstones land closer to the center of circulation. This study examines the size-sorting effect and compares a modeled hailswath to documented hailswaths. The calculation of this size-sorted hailswath may have operational use in forecasting where specific warnings can be issued containing detailed information about the size of hail that may reach the affected localities.
Poster Session 2, Cloud Physics Poster Session II
Wednesday, 12 July 2006, 5:00 PM-7:00 PM, Grand Terrace
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