The Severe Thunderstorm Electrification and Precipitation Study (STEPS) too place between 17 May 2000 and 20 July 2000 in eastern Colorado and western Kansas. One goal of STEPS is to find a relationship between the microphysics and dynamics of severe storms on the High Plains and their unusual po... Show moreThe Severe Thunderstorm Electrification and Precipitation Study (STEPS) too place between 17 May 2000 and 20 July 2000 in eastern Colorado and western Kansas. One goal of STEPS is to find a relationship between the microphysics and dynamics of severe storms on the High Plains and their unusual positive cloud-to-ground lightning production. A severe storm observed on 29 Jun 2000, which produced large hail, frequent positive cloud-to-ground lightning, and an F1 tornado, is the focus of this research. Measurements from three Doppler radars were combined to produce the three-dimensional winds in the storm. Radial components of the wind fields relative to the three Doppler radars were combined to produce the three-dimensional winds in the storm. Bulk precipitation types (e.g. rain, hail) were objectively determined using the multi-parameter variables available on two of the radars. The Doppler-derived kinematic fields were then compared with the microphysical classifications over a nearly three-hour period to look for trends in their evolution. The updraft of this storm fluctuated, with speeds up to nearly 50 m s^-1. The peaks in hail production aloft, largely around -10°C, were well correlated with peaks the in the frequency of positive cloud-to-ground lightning flashes. This fits with some experimental work that shows positive charging in ice-ice collisions around -10°C. The results of this study will be used to help determine the electrification mechanisms of severe storms that produce predominantly positive cloud-to-ground lightning. Show less
