A Sferic Rate Azimuth-Profile of the 1955 Blackwell, Oklahoma, Tornado

Abstract

A new analysis is presented on sferics data recorded during the severe storm which produced the Blackwell, Oklahoma, tornado of 1955. Film records taken from a 150-kHz sferics direction finder permit analysis not only of total count rates, but also of azimuth-of-arrival distribution and, in part of the data, relative intensity distribution as well. The results, presented as azimuth-profile plots, yield more information about the electrical activity in the storm than can be drawn from nondirectional count rates alone. High sferic count rates are found to originate not from an isolated region within the storm; rather they represent an intense electrification of the entire storm. The most intense sferics do, however, appear to peak about a core of strongest convective activity. Sferic rate tends to fluctuate with a period of several seconds and is largely unaffected by touchdown of the tornado. It is proposed that this type of recording and analysis can contribute to the understanding of tornado-bearing storms, and to the design of detection and warning systems.