We investigated the impact of variations in oceanic preexisting conditions on predictions of Typhoon Hai-Tang (2005) by using a coupled atmosphere-ocean model with 6-km horizontal resolution and providing the oceanic initial conditions on 12 July from 1997 to 2005 to the model. Variations in oceanic preexisting conditions caused variation in predicted central pressure of nearly 18？hPa at 72？h, whereas sea-surface cooling (SSC) induced by Hai-Tang caused a predicted central pressure difference of about 40？hPa. Warm-core oceanic eddies up to a few hundred kilometers across and a deep mixed layer climatologically distributed in the western North Pacific led to high mixed-layer heat potential, which increased latent heat flux, water vapor, and liquid water contents around Hai-Tang's center. These increases were closely associated with Hai-Tang's intensification. SSC negatively affected the eyewall, whereas variations in oceanic preexisting conditions remarkably affected spiral rainbands and the magnitude of SSC. 1. Introduction Advances in ocean data assimilation systems have enabled us to further understand tropical cyclone (TC) activity and the ocean response at weather-forecasting as well as seasonal to climate time scales. The relationships between TC activity and variations in the global ocean are of growing interest on seasonal to climate time scales. In contrast, TC-induced sea-surface cooling (SSC), the decrease in sea-surface temperature (SST) during and after the passage of a TC in general, is a well-known ocean response to a TC on a weather-forecasting scale. Previous studies reported that SSC varied depending on oceanic preexisting conditions [1] as well as on TC intensity and translation speed [2]. However, the dynamic and thermodynamic processes associated with SSC remain controversial [1, 3, 4] although vertical turbulent mixing and upwelling are known to be important [2]. According to our current understanding of the relationship between TC activity and ocean thermal forcing, not only SST but also temperature and salinity profiles in the upper ocean are important for determining TC intensity, whereas SSC slightly affects TC track prediction [5]. TC heat potential (TCHP), a measure of the oceanic heat content from the surface to the C isotherm depth (Z26), is highly correlated with TC intensity in the western North Pacific (WNP) on seasonal to climate time scales [6, 7]. TCs tend to rapidly intensify in the WNP when they pass over a region with a high TCHP and a deep Z26. Providing accurate oceanic preexisting conditions as oceanic initial
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