Monday, 3 November 2014
Capitol Ballroom AB (Madison Concourse Hotel)
Previous research suggests that storm-relative air flow could be as important as updraft speed in hail formation and growth. The purpose of this study is to determine how the hodograph structure of supercell thunderstorm environments affects the diameter of hailstones and the area impacted by a hail event. Simulations are performed using the Bryan Cloud Model Version 1 (CM1), a high-resolution storm-scale numerical model. The baseline simulation is the standard idealized supercell that uses the Weisman and Klemp (1982) sounding as the thermodynamic profile and a quarter-circle hodograph. To investigate how slight alterations to the wind profile at various heights yielded different sizes, shapes and locations of hail swaths at the surface, various parameters of the quarter-circle hodograph shape are varied. The changes in hodograph shape and maxima yield significant differences in the spatiotemporal dimensions of the simulated hail swaths at the surface. The standard model output includes two products, maximum hail mass-maxing ratio and total number concentration mixing ratio. In addition, new metrics are developed to evaluate differences in hail swaths. The weighted fall speeds of both the hail number concentration and mass-mixing ratio are combined to produce a useful metric that serves as a proxy for hail kinetic energy. Using the simulated particle size distributions we determine the number concentration of hail-stones that exist in excess of a defined diameter threshold. These results will be useful in analysis of future hail storms using high-resolution models to better assess risks and damages to life and property.
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