Cold surges along the Front Range of the Rocky Mountains : development of a classification scheme

• Published in: Meteorology and atmospheric physics Vol. 48; no. 1-4; pp. 249 - 271
• Main Authors: MECIKALSKI, J. R, TILLEY, J. S
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Wien Springer 01.01.1992; New York, NY
• Subjects: Convection, turbulence, diffusion. Boundary layer structure and dynamics; Earth, ocean, space; Exact sciences and technology; External geophysics; Meteorology; Rocky Mountains; North America; America; Front Range, North America; Cold air; Air flow; Anticyclone; Atmospheric front; Surge; Classification; Cold front; Relief effect
• ISSN: 0177-7971; 1436-5065
• DOI: 10.1007/BF01029572

A classification scheme for cold surges occurring along the Front Range of the Rocky Mountains has been developed using NMC surface and upper air data. A separation is seen in the data between cases with ``parent'' anticyclones that moved from Canada south into the United States (northern type) and those which moved from the eastern Pacific Ocean east into the central U.S. (western type). The northern surges are further broken down into three types, A, B and B', when the degree of southward motion of the anticyclone and the leading edge of the cold air is considered. An anticyclone movement south of 40 degrees N distinguishes type A, while anticyclone tracks remaining north of 40 degrees N characterize types B and B'. The leading edge of the surge (the surge line) associated with the type A anticyclone travels south of 25 degrees N, while the type B anticyclones produce two distinct surge line movements, one remaining north of 25 degrees N and the other moving south of 25 degrees N. It is not possible to break down the western surges into distinct types. As a rule, the anticyclones associated with western surges remain between 50 degrees N and 30 degrees N, with the surge line moving south to similar to 18 degrees N on average. Though the classification scheme is developed in a relatively subjective manner, the statistical robustness of the scheme is verified through application of the nonparametric Mann-Whitney test. Results of the test clearly provide support for the division of the surges that was obtained.