A Jet-Centered Framework for Investigating High Plains Winter Storm Severity

Abstract

Abstract This study utilizes a winter severity index (WSI) to characterize the impacts of High (Great) Plains winter storms during the 2006/07–2018/19 winter seasons across Nebraska and the Colorado Front Range. Winter storms are specifically defined based on the severity of their meteorological impacts and are required to influence a majority of Department of Transportation (DOT) districts within both states. Following their identification, winter storms are examined using a jet-centered framework based on the two leading modes of North Pacific jet (NPJ) and North Atlantic jet (NAJ) variability. The analysis reveals that a retracted or equatorward-shifted NPJ establishes a highly amplified flow pattern conducive to cyclogenesis over the central United States, while a poleward- or equatorward-shifted NAJ favors the development of a strongly baroclinic environment across the study region that serves as a focal region for cyclogenesis and precipitation. Composite analyses of winter storms that rank in the top 25% and bottom 25% in terms of their aggregate WSI are also performed to identify characteristics of the synoptic-scale evolution that discriminate between “high impact” and “low impact” events, respectively. High-impact events are found to feature a more amplified upper-tropospheric flow pattern over the eastern North Pacific and western United States relative to low-impact events, which subsequently favors stronger cyclogenesis over the southern plains. The integration of jet regimes with winter storm severity metrics as part of this study offers the potential to enhance impact-based decision support services and provide the weather enterprise, and its stakeholders, with critical life-saving information.