Ma-on is the name of a mountain in Hong Kong. Ma-on formed from a cluster of thunderstorms in the vicinity of Guam on September 29. The small system eventually trekked west-northwesterly. After days of sputtering across the western Pacific, Tropical Depression 26W formed on October 4, and quickly became named Tropical Storm Ma-on. The system became stationary approximately 650 nm southeast of Okinawa, Japan. PAGASA named the cyclone Rolly when it passed the 135th meridian. On the 5th, a northward drift ensued while well southeast of Okinawa. Upon reaching typhoon intensity late on the 06th, Ma-on turned northwest and ultimately became the sixth super typhoon of the year on the 8th while 250 miles southeast of Okinawa. The typhoon become the worst storm to hit eastern Japan in over ten years, only a week after Typhoon Meari had made landfall in that nation. Ma-on started to accelerate northeastward and its eye began to shrink in diameter and became more ragged. A slow weakening trend materialized as it entered the early stages of extratropical transition. Recurving northeast at a high rate of translation, Ma-on made landfall on the Izu Peninsula, Honshū, Japan, late on the 9th with maximum sustained winds of 105 kts/120 mph as a Category 3 typhoon. Ma-on weakened rapidly and was downgraded to a tropical storm by the 10th, and quickly completed its transformation into a nontropical low. The remnant system moved more east-northeastward away from eastern Japan before slowing its motion 1100 miles southeast of Hokkaidō.
Ma-on was one of the most powerful storms to strike eastern Japan over the last ten years. The highest wind gust reported was 151 mph/67.6 m/s in Irouzaki late on the 9th. The lowest pressure was also recorded at Irouzaki; 964 mb late on the 9th. The typhoon left at least six people dead, and three persons were reported missing. Plane, train and ferry services nationwide were disrupted, stranding thousands of travellers. Heavy downpours also disrupted practice and qualifying sessions for Formula One's Japanese Grand Prix in Suzuka, with the event featuring qualifying and the race in a single day as a result. The highest storm total amount was noted at Omaezaki, where a 413 mm deluge was seen between late on the 6th and 9th, with 360 mm falling in a 24 hour period. Rescuers on boats plucked dozens of residents from waterlogged homes in Shizuoka Prefecture. Damages from the storm amounted to $603 million (2004 USD).