This paper describes the results of the meteorological analysis when the maritime casualty of the sailing T/S Kaiwo Maru occurred on October 20, 2004. She anchored in the left semicircle of typhoon, in which winds were expected to be lower than in the right semicircle. From the Japan Meteorological Agency analysis data, it is found that Typhoon 0423 changed to the extratropical cyclone at the time of the accident and had stronger winds in the left semicircle than in the right semicircle. It is moreover found that the gale with higher wind speed than 30m/s in the left semicircle was caused by the advection of cold air mass from the north, which intensified the pressure gradient and also deformed the atmospheric pressure pattern in the cold air mass region in the changing process to the extratropical cyclone. This is the primary factor to cause such strong winds. As the secondary factor, winds were also strengthened by about 1 to 2m/s in the casualty area due to the effects of geographical features in Toyama Bay.
