熱帶氣旋形成警報
Late on October 10, a tropical disturbance formed east-southeast of Guam. There were favorable environmental conditions, such as low vertical wind shear, good upper-level divergence and poleward outflow. The system began to significantly develop on October 12, prompting the Joint Typhoon Warning Center (JTWC) issuing a Tropical Cyclone Formation Alert at 09:00 UTC. Several hours later, the Japan Meteorological Agency (JMA) began monitoring the system as a tropical depression. Early on October 13, JTWC also classified the system as a tropical depression and designated it "15W".