Are We Reaching the Limit of Tropical Cyclone Track Predictability in the Western North Pacific?

Abstract

AbstractThe annual-mean position errors (PE) of tropical cyclone (TC) track forecasts from three forecast agencies (RSMC-Tokyo, CMA, and JTWC) are analyzed to document the past improvements and project future tendency in track forecast accuracy for TCs in the western North Pacific. An improvement of 48 h (2-day) in lead time has been achieved in the past thirty years, but with noticeable stepwise periods of improvements with superposed short-term fluctuations. The stepwise improvement features differ among the three forecast agencies, but are highly related to the development of objective forecast guidance and the application strategy. As demonstrated by an exponential model for the growth of PEs with lead time for TCs of tropical storm category and above, the improvements in the past ten years have mainly been due to the reduction in analysis errors rather than the reduction in the error growth rate. If the current trend continues, a further 2-day improvement in TC track forecast lead times may be projected for the coming fifteen years up to 2035, and we certainly have not reached yet the limit of TC track predictability in the western North Pacific.