The progenitor to Typhoon Nanmadol was first noted by the Joint Typhoon Warning Center (JTWC) as an isolated cluster of thunderstorms roughly 290 km (180 mi) south-southwest of Pohnpei at 2200 UTC on November 27, 2004.
With convection consolidating about a potential center of circulation, the Japan Meteorological Agency (JMA) classified the broad system as a tropical depression the following day.
Rapid development of storms and organization ensued following classification, spurred by favorable conditions.
Tracking northwestward due to the presence of a nearby subtropical ridge to its north, the depression continued to strengthen, reaching tropical storm intensity on November 29 while 860 km (530 mi) south-southeast of Guam.
At this point the tropical cyclone was assigned the name Nanmadol.

Conducive atmospheric conditions around Nanmadol on November 29 led to the development of a central dense overcast, followed shortly thereafter by the formation of an eye.
Nanmadol was upgraded to severe tropical storm intensity at 0000 UTC on November 30 and became a typhoon twelve hours later, tracking near Satawal, Woleai, and Yap State during this intensification phase.
Following the upgrade to typhoon status, intensification briefly slowed but continued soon thereafter.
At 0600 UTC on December 1, Nanmadol reached peak intensity with maximum sustained winds of 165 km/h (105 mph) and a minimum barometric pressure of 935 mbar (hPa; 27.61 inHg), still east of the Philippines.
The typhoon maintained this strength for roughly twelve hours before slightly weakening as it neared Luzon.
At approximately 1200 UTC on December 2, Nanmadol made landfall near Casiguran, Aurora with winds of 140 km/h (85 mph).

Due to the rapid motion of Nanmadol, the typhoon crossed Luzon in under six hours, emerging into the South China Sea before 1800 UTC on December 2.
Though land interaction with the Philippines did not significantly affect the cyclone, a shortwave trough forced Nanmadol to sharply curve northward, bringing it into hostile atmospheric conditions within the Luzon Strait.
At 0000 UTC on December 3, the JMA downgraded Nanmadol to severe tropical storm status.
Increased wind shear and the advection of dry air further weakened the tropical cyclone, and by midday on December 3, the storm's center of circulation became decoupled from the rest of the convection.
At 2340 UTC that day, Nanmadol made landfall near Fangliao, Pingtung in Taiwan, becoming the first December tropical cyclone to strike the island in 108 years of record-keeping.
Roughly six hours later on December 4, the JMA determined that Nanmadol had transitioned into an extratropical cyclone.
These remnants soon merged with another low-pressure area, creating a more powerful system that later tracked over Japan.
The progenitor to Typhoon Nanmadol was first noted by the Joint Typhoon Warning Center (JTWC) as an isolated cluster of thunderstorms roughly 290 km (180 mi) south-southwest of Pohnpei at 2200 UTC on November 27, 2004. With convection consolidating about a potential center of circulation, the Japan Meteorological Agency (JMA) classified the broad system as a tropical depression the following day. Rapid development of storms and organization ensued following classification, spurred by favorable conditions. Tracking northwestward due to the presence of a nearby subtropical ridge to its north, the depression continued to strengthen, reaching tropical storm intensity on November 29 while 860 km (530 mi) south-southeast of Guam. At this point the tropical cyclone was assigned the name Nanmadol.
Conducive atmospheric conditions around Nanmadol on November 29 led to the development of a central dense overcast, followed shortly thereafter by the formation of an eye. Nanmadol was upgraded to severe tropical storm intensity at 0000 UTC on November 30 and became a typhoon twelve hours later, tracking near Satawal, Woleai, and Yap State during this intensification phase. Following the upgrade to typhoon status, intensification briefly slowed but continued soon thereafter. At 0600 UTC on December 1, Nanmadol reached peak intensity with maximum sustained winds of 165 km/h (105 mph) and a minimum barometric pressure of 935 mbar (hPa; 27.61 inHg), still east of the Philippines. The typhoon maintained this strength for roughly twelve hours before slightly weakening as it neared Luzon. At approximately 1200 UTC on December 2, Nanmadol made landfall near Casiguran, Aurora with winds of 140 km/h (85 mph).
Due to the rapid motion of Nanmadol, the typhoon crossed Luzon in under six hours, emerging into the South China Sea before 1800 UTC on December 2. Though land interaction with the Philippines did not significantly affect the cyclone, a shortwave trough forced Nanmadol to sharply curve northward, bringing it into hostile atmospheric conditions within the Luzon Strait. At 0000 UTC on December 3, the JMA downgraded Nanmadol to severe tropical storm status. Increased wind shear and the advection of dry air further weakened the tropical cyclone, and by midday on December 3, the storm's center of circulation became decoupled from the rest of the convection. At 2340 UTC that day, Nanmadol made landfall near Fangliao, Pingtung in Taiwan, becoming the first December tropical cyclone to strike the island in 108 years of record-keeping. Roughly six hours later on December 4, the JMA determined that Nanmadol had transitioned into an extratropical cyclone. These remnants soon merged with another low-pressure area, creating a more powerful system that later tracked over Japan.
Typhoon Nanmadol (2004)