Tropical cyclone predictability shaped by western Pacific subtropical high: integration of trans-basin sea surface temperature effects

Abstract

Sea surface temperature (SST) anomalies in the Pacific, Indian and Atlantic oceans were suggested to explain inter-annual variability of tropical cyclone (TC) activity over the western North Pacific (WNP). Here we show that the influences of these “trans-basin” SST anomalies in the three oceans can be collectively understood via two leading modes of variability of WNP subtropical high (WNPSH). The first mode, which is forced by SST anomalies in the eastern-central Pacific and tropical Atlantic, can shift TC formation locations southeastward/northwestward, but has insignificant influence on the total TC genesis number, albeit affects the TC tracks, total number of tropical storm days, and power dissipation index (PDI). The second mode, which is a coupled ocean–atmosphere mode associated with a dipole SST anomaly in the Indo-Pacific warm pool, has a significant control on the total TC genesis number. A set of physics-based empirical models is built to predict the two WNPSH modes and TC activity (genesis number, tropical storm days and PDI) in the peak TC season (July–September) with preceding season trans-basin SST predictors. The predictions capture very well the inter-annual variabilities of the WNPSH and reasonably well the variability of WNP TC activity. These results thus establish a unified framework to understand and forecast the inter-annual variability in TC activity over the WNP.