Long-Lived Tornadic Supercell over Colorado and Wyoming, 22 May 2008

Abstract

On 22 May 2008, a slow-moving, meridional trough led to widespread severe weather across the Great Plains, Front Range Urban Corridor of Colorado and Laramie Mountains of Wyoming. The most damaging storm developed near the Denver International Airport and quickly became tornadic. A large tornado occurred with this storm that was responsible for EF3 damage in the town of Windsor, CO. After some weakening, the storm intensified and produced large hail and at least one tornado from the Wyoming-Colorado border northwestward to Laramie, WY. As the storm moved through differing elevations (4700 to 8700 ft (1430 to 2650 m), it also encountered markedly different meteorological environments, making this tornadic event particularly interesting and rare. In addition to the official Storm Data, this study will provide supplementary storm documentation based on accounts of local residents. The key synoptic and mesoscale features as well as shear and instability parameters are presented, with an emphasis on observational data.
 Additionally, in order for forecasters to gain an understanding of the high-elevation severe storm environment, a comparison is made with relatively low-elevation environments. The importance of assessing the contributing factors to equivalent potential temperature is demonstrated. Recommendations are made for forecasting severe weather at high-elevation locations. Analysis of equivalent potential temperature is critical when assessing surface data over high-elevation areas, rather than arbitrary judgment (i.e., “it’s too cold”) based on surface temperature and dewpoint.