A remarkable sea surface cooling event was observed in the north western Pacific off Japan coast, which is known as the Tohoku Area, by using well-calibrated satellite sea surface temperature images, when typhoons T8914 and T8915 passed over the Tohoku Area in August 1989. The sea surface cooling maximum reached up to 9 ¿C, which is much larger than that reported in the previous studies. The corresponding hydrographic data show that the sea surface cooling state is closely related with the ocean structure in the Tohoku Area; the larger sea surface cooling occurs in the Oyashio area. The numerical experiments taking account of the ocean structure show that the surface cooling maximum is 3--4 times larger in case of the Oyashio profile than that of the Kuroshio profile and clarify the mechanism of the sea surface cooling. ¿ 1998 American Geophysical Union