Tornadogenesis by nonprecipitation induced wind shear lines.

Abstract

Five tornadoes occurred within a 40 min period on 18 May 1984 in eastern Colorado. The evolution of these tornadoes was documented by a single Doppler radar, research aircraft, mesonetwork and chase team. All five of these tornadoes occurred along two wind shift lines near the point where the lines intersected. These lines were of synoptic scale origin-a cold front and a trough line. The low-level echo structure and wind field associated with the parent storm of the two larger tornadoes closely resemble those described in the literature for supercell storms. While the environmental vertical wind shear was less than normally expected for supercell storms, it is believed that the preexisting boundaries created the necessary vorticity and vorticity production mechanisms for tornadogenesis. -from Author