A Numerical Investigation of East Coast Cyclogenesis during the Cold-Air Damming Event of 27–28 February 1982. Part I: Dynamic and Thermodynamic Structure

Abstract

On 27?28 February 1982 cyclogenesis occurred along a Carolina coastal front. As the relatively weak low pressure center developed and moved northeastward along the front, up to 30 cm of snow fell in 12 hours in the mountains of western Virginia and moderate icing persisted throughout 27 February in the Carolinas. On 28 February the mesoscale cyclone intensified more rapidly, turned east-northeast after passing Cape Hatteras, and gradually became a typical synoptic scale oceanic storm. A nested version of the Penn State/NCAR mesoscale model with 35-km fine-mesh resolution is used to simulate the prestorm environment and subsequent cyclogenesis during a 36-h period. Evaluation of the numerical results indicates that the model successfully reproduced most principal synoptic and mesoscale features associated with this complex east coast cyclogenesis case, including storm path and intensification, coastal front structure, cold-air damming, circulations induced by a polar jet streak, low-level jets, and precipitation. In particular this study 1) provides an in-depth numerical examination of a case of east coast cyclogenesis in which entrance region jet streak dynamics provides the dominant upper-level support white only a weak baroclinic wave was approaching from the west, 2) reveals the existence of two moist airstreams fed by onshore flow from the marine boundary layer east of the coastal front (a southeasterly low-level jet and a rapidly rising ?feeder? supporting the ascending branch of the polar jet streak's entrance circulation), 3) explores the origin, history, and significance of these moist airstreams to cyclogenesis (the southeasterly low-level jet supports inland precipitation while the rapidly ascending airstream contributes to heavy precipitation and failling pressure along the coast), and 4) demonstrates that both airstreams are well developed very early during the cyclogenesis before the midlevel baroclinic wave reaches the coast.