Large-Scale Circulation Variability over the Tropical Western North Pacific. Part II: Persistence and Transition Characteristics

Abstract The variability of the large-scale circulation over the tropical western North Pacific is described within a framework defined by recurrent 700-mb circulation patterns that were defined by a fuzzy cluster analysis. Individual cluster patterns (defined in Part 1), which represent instantaneous depictions of the circulation variability, define favorable and unfavorable regions for tropical cyclone genesis and preferred track types. The fuzzy cluster coefficients, which describe the time variability of 700-mb large-scale circulation anomalies, are used to identify the basic persistence properties of the recurrent, anomalous circulation patterns. It is found that recurrent circulation patterns that are defined by small anomalies (i.e., close to the center of the cluster analysis phase space) are less persistent than recurrent patterns that represent distinct circulation anomaly patterns. Furthermore, the persistence of a particular sequence of anomaly maps that pass through a cluster is dependent upo...