What Has Controlled the Poleward Migration of Annual Averaged Location of Tropical Cyclone Lifetime Maximum Intensity Over the Western North Pacific Since 1961?

The long-term tendency of the average latitude at which tropical cyclones (TCs) reach their lifetime maximum intensity (LMI) over the western North Pacific (WNP) is investigated in this study. Despite the post-1961 significant poleward shift in the annual mean LMI latitude, the migration rate is nonuniform on decadal timescales, having an insignificant trend and a significant increasing trend before and after 1980, respectively. Interdecadal fluctuations of TC genesis latitude (phi(G)) as well as increases in latitudinal distance between genesis position and LMI location (Delta phi) are both responsible for the observed LMI latitude trends. The former is linked to the Interdecadal Pacific Oscillation (IPO), which favors TCs forming in the northwestern (southeastern) quadrant of the WNP in negative (positive) IPO phases. The latter primarily results from the continuous warming of WNP sea surface temperature, which further increases the maximum potential intensity and extends the region favorable for TC development to higher latitudes.