Around 1800 UTC 29 May 1995 a line of thunderstorms developed from central New York southward to Virginia. Many of the cells along this line quickly took on supercell characteristics, obtaining persistent rotating updrafts. As the cells matured they produced a variety of severe weather including wind damage, large hail, and tornadoes. The cells which developed in Pennsylvania, formed just east of the Weather Surveillance Radar-1988 Doppler (WSR-88D) and remained within range of the WSR-88D through most of their life time. The first severe supercell of the day formed within 30 km of the radar providing a unique opportunity to observe the structure of a mini-supercell thunderstorm using WSR-88D archive II data.
These storms formed in an environment more typical of a mid-Western severe weather outbreak resulting in a line of supercell thunderstorms, which were similar, but smaller than, those in the Midwest. In Pennsylvania, WSR-88D observations indicated that virtually every cell along the line obtained rotation, 80% of the rotating cells produced some form of severe weather, and but only 20% of the observed supercells produced tornadoes.
This paper will show the characteristics of eastern United States mini-supercel
thunderstorms using WSR-88D archive II data. These radar data, along with
observational data, spotter reports, and model data will be shown to present the
environment in which these storms occurred and how they can be forecast.