Contributions of orographic and diabatic processes to rapid frontogenesis over the western United States

Intense, rapidly developing cold fronts occur over the Intermountain West several times per year, and are accompanied by dramatic temperature falls and strong winds ( > 25 m/s). This poster examines the structural and dynamical evolution of a front that made landfall as a weak occlusion on the morning of 25 March 2006. As it moved inland and traversed the Sierra Nevada its vertical structure was significantly modified, leaving almost no discernible frontal passage in the lee of the barrier. The front then progressed across Nevada, with diabatic processes and confluence in the lee of the Sierra Nevada contributing to rapid redevelopment. The front arrived in northern Utah just 15 h after landfall accompanied by temperature falls of 14°C in 2 h (8°C in 15 min). At its maximum intensity lowland wind gusts exceeded 35 m/s, bringing down trees and power lines, and blowing the roofs off houses. Through observational analysis and numerical modeling, this poster investigates the orographic and diabatic mechanisms of frontogenesis specific to this region of the world.