An Updated Climatology of Extratropical Cyclones in Colorado
McKenzie Larson, University of Colorado Boulder
Previous studies of surface extratropical cyclone (i.e., low-pressure systems) characteristics and predictability focus predominantly on coastal North America due to their larger population densities. Yet, the Colorado Front Range (CFR) located to the east of the Rocky Mountains is also a favorable region for surface cyclogenesis. Consequently, this study focuses on cyclone characteristics across the comparatively understudied CFR. This region’s distinctive location in the center of the continental United States and complex topography contributes to unique forecast challenges, including uncertainty in the prediction of storm intensity, cyclone location, and areas of heavy precipitation. The operating status of schools, restaurants, government offices, and airports are all affected by these forecasts, leading to profound societal and economic impacts. To begin investigating the characteristics of cyclones and their predictability along the CFR, this study performs a climatological analysis of cyclones that will serve as a baseline for future analyses into cyclone predictability and the effects of climate change in this region.
Cyclones during 1980 to 2021 within the vicinity of the CFR were discerned within the ERA5 reanalysis using a cyclone identification method adopted from previously published work.1,2 This unique dataset facilitated an analysis of the monthly and seasonal frequency of CFR cyclones, in which few significant trends were found over the 42-year period of study. Self-Organizing Maps (SOMs) trained using mean sea-level pressure anomalies from ERA5 were subsequently used to examine the variability in large-scale weather regimes conducive to cyclogenesis along the CFR. Future work will investigate the extent to which the characteristics of cyclone environments (i.e., frontal structure, moisture sources, upper-level jet stream structure, etc.) vary as a function of the prevailing weather regime.
References:
1Sprenger, M., Fragkoulidis, G., Binder, H., Croci-Maspoli, M., Graf, P., Grams, C. M., Knippertz, P., Madonna, E., Schemm, S., Škerlak, B., & Wernli, H. (2017). Global Climatologies of Eulerian and Lagrangian Flow Features based on ERA-Interim, Bulletin of the American Meteorological
Society, 98(8), 1739-1748.
2Wernli, H., & Schwierz, C. (2006). Surface Cyclones in the ERA-40 Dataset (1958–2001). Part I: Novel Identification Method and Global Climatology, Journal of the Atmospheric Sciences, 63(10), 2486-2507.
Abstract Author(s): McKenzie L. Larson, Andrew C. Winters