On August 26, the tropical cyclone that was once Hurricane Ilsa degenerated into a remnant low-pressure area, about 1,200 miles (1,950 km) west of the southern tip of the Baja California Peninsula. The remnants of Ilsa drifted northwestward through the stratocumulus cloud field in the eastern north Pacific Ocean. At the same time, a mid-tropospheric trough slowly intensified while gradually undergoing cyclogenesis to develop into a cold-core upper-level low. Early on August 31, a low-level circulation formed within the upper-level low about 930 miles (1,500 km) northeast of Hawaii; at that time, the circulation and the remnants of Ilsa were located within 370 miles (600 km) of each other. The cold-core low rapidly intensified as convection increased, and late on August 31, it absorbed the remnants of Ilsa, which influenced the development of the system. Convection steadily organized as it tracked westward, and it is estimated it transitioned into a subtropical depression by 18:00 UTC on September 1.