A climatology of sea surface temperature and the maximum intensity of western North Pacific tropical cyclones

Using a 31-year (1960-1990) sample of western North Pacific tropical cyclones and monthly mean sea surface temperature (SST) for each year, an empirical relationship between SST and the maximum intensity of western North Pacific storms is determined and used to calculate the relative intensity, a measure of how close a storm reaches its maximum potential intensity. The analysis method in this study follows that by DeMaria and Kaplan (1994b) and results are compared with observations over the North Atlantic and theoretical studies. Similar to previous studies, an upper bound of storm intensity for a given SST was determined. It is shown that a larger fraction of Pacific storms are observed over warm waters than Atlantic storms and the maximum potential intensity of Pacific storms tends to be stronger than that of Atlantic storms or theoretically calculated storms. The analyses of the relative intensity at the time of each storm's life-time maximum intensity indicate that the maximum intensity of Pacific storms is well below the maximum potential intensity. The average relative intensity of the total sample is 37 % (47 %) when the regression curve for the maximum (99th) intensity percentile is used to compute the relative intensity, implying that environmental influences appear to be more important than SST in determining the maximum intensity of Pacific storms. The average relative intensity of late-season storms tends to be, as in the Atlantic, larger than that of early-season storms, and the yearly-averaged relative intensity shows to some extent interannual variability but with little correlation either with quasi-biennial oscillation or with El Nino.