On August 20, a tropical depression formed to the west of Mariana Islands. On the next day, the JMA designated the system as Tropical Storm Bailu, and the JTWC classified the system as Tropical Depression 12W. Bailu gradually intensified over the Philippine Sea. At 13:00 TST (05:00 UTC) on August 24, Bailu made landfall over Manzhou Township, Pingtung County, Taiwan.