The Teton-Yellowstone tornado of 21 July 1987

Abstract

The Teton-Yellowstone Tornado, rated F4, crossed the Continental Divide at 3070 m, leaving behind a damage swath 39.2 km long and 2.5 km wide. A detailed damage analysis by using stereo-pair and color photos revealed the existence of four spinup swirl marks and 72 microburst outflows inside the damage area. The tornado was spawned by a mesocyclone that formed at the intersection of a mesohigh boundary and a warm front. The parent cloud of the tornado, tracked on eight infrared-temperature maps from GEOS East and West, moved at 25 m s-1 and the number of cold temperature pixels below -60°C reached a distinct peak during the tornado line. -from Author