Typhoon Maemi formed on September 4 from the monsoon trough in the western Pacific Ocean . It slowly intensified into a tropical storm while moving northwestward , and Maemi became a typhoon on September 8 . That day , it quickly intensified due to favorable conditions , developing a well @-@ defined eye and reaching peak maximum sustained winds of 195 km / h ( 120 mph ) . While near peak intensity , Maemi was decelerating and began turning to the north @-@ northeast . The eyewall soon after passed over the Japanese island of Miyako @-@ jima on September 10 , producing the fourth lowest pressure on record in Japan after a pressure of 912 mbar ( 26 @.@ 9 inHg ) was recorded . With warm waters , Maemi was able to maintain much of its intensity before it made landfall just west of Busan , South Korea on September 12 . On Jeju Island , Maemi produced a peak wind gust of 216 km / h ( 134 mph ) and a minimum pressure of 950 mbar ( 28 inHg ) , both setting records for the country , and making it the most powerful typhoon to strike South Korea since record @-@ keeping began in the country in 1904 . The typhoon became extratropical in the Sea of Japan the next day , although the remnants persisted for several more days , bringing strong winds to northern Japan .