P1.5 A climatology of strong cold fronts over the western United States

Monday, 1 August 2005
Regency Ballroom (Omni Shoreham Hotel Washington D.C.)
Jason C. Shafer, Univ. of Utah, Salt Lake City, UT; and W. J. Steenburgh

This poster will detail the results from a 25-year climatology (1979-2003) of strong cold fronts at 77 locations over the western United States. Strong cold fronts were identified by meeting all of the following criteria: 2h pressure rises of 3 hPa or greater, 2h temperature falls of 7°C or larger, and 700-hPa baroclinity greater than or equal to 7°C over 500km. Results from the climatology revealed a strong diurnal and seasonal cycle, where the maximum frequency of strong cold fronts peaked around 2-4 h after maximum daytime heating, and the maximum seasonal frequency peaked during the late spring and early summer.

This poster will describe characteristics of the pre- and postfrontal environment, and the relationship of wind and precipitation relative to the events. For example, approximately 50% of the events were associated with measurable precipitation within +/- 12 hours of frontal passage; however, approximately 75% of the events were associated with measurable precipitation during their history. This poster will also explore the multi-scale processes behind the rapid development of strong cold fronts, including the role of diabatic frontogenesis and the boundary layer.

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