The Dynamics of Large-Scale Cyclogenesis over the North Pacific Ocean

Abstract Earlier studies of persistent large-scale flow anomalies have been extended, with the aim of identifying the primary mechanisms for persistent anomaly development. In this study the focus is on wintertime cases of persistent cyclonic flow anomalies over the North Pacific. These cases are typically manifested by an abnormally intense cyclonic circulation extending over the North Pacific basin, an unusually strong and eastward-extended East Asian jet, and a well-defined Pacific-North American teleconnection pattern. We have conducted extensive diagnostic analyses in order to determine the mechanisms responsible for development. In particular, these diagnostics examine the processes influencing the time evolution of eddy potential enstrophy and potential vorticity anomalies. The cases are preceded by a buildup of anomalously high potential vorticity air at upper levels over eastern Asia. This high potential vorticity air is initially advected eastward in association with synoptic-scale cyclogenesis ...