Atmospheric Sensitivity to SST near the Kuroshio Extension during the Extratropical Transition of Typhoon Tokage*

It is hypothesized that the tropical-to-extratropical transition of a cyclone in the western North Pacific can be sensitive to the underlying sea surface temperature (SST) distribution. This hypothesis was tested through a case study of Typhoon Tokage using a series of high-resolution simulations by the Weather Research Forecast (WRF) numerical weather prediction model. Simulations were carried out for a control SST distribution and for SST distributions with imposed warm and cold perturbations of 1.5°C maximum amplitude in the vicinity of the Kuroshio Extension. The simulations with the warm SST perturbation yielded a cyclone slightly weaker than in the control SST case about 2 days after transition. In contrast, the cold SST perturbation case yielded a cyclone with a central pressure 10 hPa lower than in the control case at the same point in the storm’s life cycle, apparently due to its more northward track and hence closer proximity to an approaching upper-level trough and perhaps in associati...