Changes of Tropical Cyclone Size in three Oceanic Basins of the Northern Hemisphere since 2001

Abstract

In this study the latest changes of tropical cyclone size are analyzed based on linear and quadratic curve fittings of the National Hurricane Center (NHC)/Joint Typhoon Warning Center (JTWC) best track data for the radius of maximum wind (RMW), the average radius of 34-kt wind (AR34), and the storm duration index “storm days” (SD) in three oceanic basins of the North Atlantic (NATL), the Western North Pacific (WPAC) and the Eastern North Pacific (EPAC). The computations are done separately for two categories of tropical cyclones: tropical storms (TS), and hurricanes in NATL and EPAC or typhoons in WPAC (HT). The results show that the RMW trends for TS are positive in all basins, and the RMW trends for HT are positive in the NATL basin, but negative in the WPAC and EPAC basins. The AR34 changes are more complex due to the fact that they reflect not only the strength of tropical cyclones, but also the environmental conditions. The trends of two other data sets, with WPAC dataset from the Japan Meteorological Agency (JMA) and the extended best track dataset for NATL and EPAC from NESDIS/RAMMB, are also consistent with the trends derived from the 16-year best track data. The relationships between storm size and sea surface temperature anomaly and the departure from the zonal mean have also been investigated, and some statistically significant correlations are found.