In early September 2003, a monsoon trough created a tropical disturbance near Guam. The system consisted of a disorganized area of convection, or thunderstorms, in an area of moderate wind shear. By September 4, the convection was becoming better organized around a weak low-level circulation. Despite the wind shear, the system continued to develop, becoming a tropical depression north of Chuuk State. At 0200 UTC on September 5, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert, and later that day initiated advisories on Tropical Depression 15W just west of Guam. By that time, the convection had increased over the center. For the first week of its existence, the cyclone tracked generally northwestward, steered by a subtropical ridge to the north.