A case study of nonmesocyclone tornado development in northeast Colorado: similarities to waterspout formation

Abstract

This tornado develops within 20 km of the radar site under weakly forced synoptic conditions and weak tropospheric flow, and is not accompanied by a mesocyclone. The initial circulation forms near the surface at the intersection of two mesoscale boundaries and develops vertically, intensifying into an F1 tornado when it becomes collocated with the intense updrafts of a rapidly developing cumulonimbus. This tornado appears to be the land equivalent of a waterspout, and comparisons between the two vortices are made. Suggestions on how to better forecast these tornadoes are also presented. -from Authors