The eighteenth tropical cyclone and the thirteenth named storm of the 2001 Pacific typhoon season, Usagi originated from an area of convection persisted over the South China Sea on August 8.

However, the JMA, JTWC, and the CMA upgraded the system to a tropical storm, with the former naming it Usagi, shortly before making landfall on Ha Tinh, Vietnam on August 10.

[1] An area of convection developed into a weak tropical depression in the South China Sea, just west off Luzon on August 8.

By 18:00 UTC, Usagi moved inland Vietnam, just to the south of Hanoi, and therefore the JTWC issued its final advisory on the system.

[5] The Thai Meteorological Department on the neighbouring country, Thailand reported that over 176 people died due to the flash floods and landslides from the remnants of the storm, with Lom Sak District the worst affected.