Typhoon Ma-on originated from a weak low-pressure area accompanied by persistent convection, or thunderstorms, north-northwest of Guam on September 29, 2004.

Though environmental conditions featured weak wind shear and modest diffluence, favoring tropical cyclogenesis, the convection was cyclical and the system did not develop much over the following two days.

On October 3, a QuikScat satellite pass revealed a well-developed circulation while a ship 555 km (345 mi) south of the low reported 45 km/h (28 mph) winds.

[2] Twelve hours later, the depression crossed 135°E and entered the Philippine Atmospheric, Geophysical and Astronomical Services Administration's (PAGASA) area of responsibility, receiving the local name Rolly from the agency.

At 00:00 UTC on October 4, the Joint Typhoon Warning Center (JTWC) classified the system as Tropical Depression 26W; the newly designated cyclone was situated over the Philippine Sea roughly 1,145 km (711 mi) west-northwest of Guam at this time.

[1] The JTWC estimated Ma-on to have reached typhoon status around 06:00 UTC on October 6,[3] with the JMA following suit 12 hours later.

[2] Synoptic patterns changed dramatically on October 7 as a trough emerged off the coast of East China and prompted Ma-on to turn northeast.

[2] The JTWC estimated Ma-on to have been a significantly stronger storm with one-minute sustained winds topping out at 260 km/h (160 mph) at 00:00 UTC on October 8.

Convection became increasingly asymmetric with dry air impinging on the southwestern semicircle, indicating the beginning of extratropical transition.

The typhoon made landfall along the Izu Peninsula of Japan around 07:00 UTC on October 9, with winds of 150 km/h (93 mph) and a central pressure of 950 mb (hPa; 28.06 inHg).

[1][2] After losing a defined low-level circulation early on October 10,[2] Ma-on's the remnant trough continued eastward across the North Pacific.

More than a week later, by October 18, the storm moved over the Bering Sea and began to intensify rapidly as conditions favored bombogenesis of the baroclinic system.

[5] Regardless of its dominant origin the storm moved across the central Aleutian Islands with a pressure of 978 mb (hPa; 28.88 inHg) on October 17 and doubled back to the west throughout the next day.

Situated 640 km (400 mi) west of Nome, Alaska, the powerful storm subsequently weakened and slowed on October 19.

By October 20, the system filled to 980 mb (hPa; 28.95 inHg) low and reached a position 640 km (400 mi) west of Kotzebue, Alaska.

[7] As Typhoon Ma-on began turning to the north on October 8 towards Japan, the JMA warned residents in the Tōkai, Kansai, and Shikoku regions of heavy rain.

[11] The Central Japan Railway Company temporarily suspended service for the entire Tōkaidō Shinkansen line, which travels from Tokyo to Shin-Ōsaka.

[12] Practice and qualifying runs for the 2004 Japanese Grand Prix at the Suzuka Circuit, initially scheduled for October 9, were suspended until the following day.

[15] Of these storms, Ma-on was the only system to strike eastern areas of the nation directly and the second-strongest, with a landfall pressure of 950 mb (hPa; 28.06 inHg).

As the storm passed through, a low level jet formed along the east edge of the Kanto Mountains and facilitated an extreme gap flow event.

As the backside of the storm moved through, northerly winds pushed the cooler air south and allowed it to extend to higher altitudes as it paralleled the mountains along the west side of the plains.

[15] Torrential rains accompanied the storm, with several areas reporting rainfall rates in excess of 60 mm (2.4 in) per hour.

Nearly 200 landslides across the prefecture shut down large stretches of highway and rail lines, paralyzing public transportation.

[34] Additional, though minor, damage occurred in Akita,[35] Aomori,[36] Gifu,[37] Mie,[38] Niigata,[39] Shimane,[40] Tochigi,[41] Wakayama,[42] and Yamagata prefectures.

The value in Nome exceeded the previous record of 3.7 m (12 ft) in October 1992; however, the measurement at Red Dog Dock was surpassed just over two months later.

Erosion in Elim destroyed a local road and exposed the city's septic tanks and main water line.

[6] In the aftermath of the storm, on November 16, President George W. Bush signed a disaster declaration for the Bering Strait Regional Education Attendance Area and the Northwest Arctic Borough.

[48] Public assistance teams were deployed to Nome and Unalakleet on November 19 to establish a base of operations for relief and assess the impact of the storm.