Thursday, 7 October 2004
The detection of both in-cloud and cloud-to-ground lightning by instruments introduced within the last decade, have given the lightning research community the opportunity to better understand the association between storm intensity and lightning activity. The results to be presented will focus on total lightning behavior relative to storm severity on seven storms, six of which produced large hail, high winds, and/or a tornado that occurred during the Severe Thunderstorm Electrification and Precipitation Study (STEPS). The study found that the main distinguishing factor between the analyzed non-severe and severe storms was a lightning flash rate increase and a spread in radiation in the four to ten kilometer regions. Also, each of the severe storm cases produced positive cloud-to-ground lightning and experienced a lightning polarity reversal. In cases where either a tornado warning was issued or an actual tornado was reported, the polarity reversal occurred before all tornadic events. The polarity reversal itself was associated with a decrease in lightning in the mid-levels of the time-height distributions. Peak currents also increased in strength after the reversal.
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