The storm formed on September 14 east of the Philippines and moved slowly for several days, initially to the northwest, then curving to the northeast before turning westward due to a ridge to the north.

About 150,000 people evacuated their homes, and there were heightened preparations after the damaging effects of Typhoon Morakot the previous year.

In some areas of the city, the floods reached over one-story deep, inundating cars and causing about NT$3 billion (New Taiwan dollar, US$93.75 million) in industrial damage.

[2] The system gradually developed a low-level circulation and rainbands, aided by low wind shear from an anticyclone aloft.

[1] Late on September 14, the Japan Meteorological Agency (JMA)[nb 2] designated the system as a tropical depression to the east of the Philippine island of Luzon.

[3] Around the same time, the Joint Typhoon Warning Center (JTWC)[nb 3] classified the system as Tropical Depression 12W.

A nearby tropical upper tropospheric trough limited the depression's outflow to the north, although convection continued to increase.

[5] At 03:00 UTC on September 15, the Philippine-based PAGASA began warning on the system, giving it the local name Inday.

[3] As the ridge built into the East China Sea, the storm responded by turning to the northwest, and at the same time, outflow improved to the north.

[3] The thunderstorms reorganized slightly as Fanapi reached open waters, and a nearby ship reported winds of 120 km/h (75 mph).

[13] Early on September 20, the storm made a second landfall on southeastern China near Fujian and weakened further over land,[3][14] although thunderstorms persisted southeast of the circulation along the coast.

[16] The storm caused the Kaohsiung seaport in southern Taiwan to close,[17] thus delaying shipments from nearby chemical plants.

[19] Portions of the Kaohsiung Mass Rapid Transit system suspended their service,[20] and the Maokong Gondola was shut down during the storm.

[21] Ahead of the storm, officials issued landslide warnings along 61 rivers,[22] and residents in landslide-prone areas were ordered to evacuate.

[25] After the damaging impacts of Typhoon Morakot from the year prior, officials enacted enhanced preparations for Fanapi,[19] including activating over 19,000 emergency workers.

[21] Farmers also rushed to complete harvests,[27] causing a temporary drop in price due to excess supply.

The Fuzhou Changle International Airport in the province's capital city canceled 37 flights due to the storm.

[14] While moving toward Taiwan, Fanapi affected the southernmost islands of Japan, bringing heavy rainfall to Okinawa Prefecture.

[43] Flooding shut down 10 petrochemical plants in Kaohsiung,[37] causing NT$3 billion (New Taiwan dollar, US$93.75 million) in industrial damage.

[44] Also in the city, a nursing home was flooded while residents were inside, forcing firemen and rescuers to evacuate the senior citizens; due to inadequate staffing during the storm, the facility was later shut down.

[25] Across Taiwan, 111 people were injured,[25] mainly due to broken glass, and some were blown off motorcycles by high winds.

[53] The storm brought heavy rainfall to southern China, with six counties in Fujian Province reporting over 200 mm (7.9 in) of precipitation in 23 hours.

[31] However, damage was heaviest in neighboring Guangdong,[57] where the storm's heavy rainfall caused widespread mudslides in the western mountainous regions.

[14] In response to the Taiwan flooding in Kaohsiung, officials deployed 7,888 troops to the southern portion of the island to assist in rescue and recovery work.

[41] Soldiers also set up five medical centers,[25] and utilized amphibious vehicles to rescue people in flooded areas.

[59] About 1,000 soldiers worked to clean debris and animal carcasses from the reservoir providing drinking water to Maoming.

[73] The name Fanapi was retired at the 43rd annual meeting of ESCAP/WMO Typhoon Committee in Jeju, South Korea, in January 2011.