Typhoon Chataan - Meteorological History

Meteorological History

On June 27, 2002, the monsoon trough spawned a tropical disturbance southwest of Pohnpei. The system rapidly organized that day, and at 2000 UTC the Joint Typhoon Warning Center (JTWC) issued a tropical cyclone formation alert. Early on June 28, the Japan Meteorological Agency (JMA) classified the system as a tropical depression near the Mortlock Islands in the Federated States of Micronesia; around the same time, the JTWC also initiated storm advisories. Early on June 29, the JTWC upgraded the system to Tropical Storm 08W, and shortly thereafter the JMA named the system Tropical Storm Chataan. After moving northwestward, the storm turned to the east, resuming a northwest track on June 30 due to a subtropical ridge to the north. The track was erratic because the storm had not yet separated from the monsoon trough. By June 30, Chataan had steadily strengthened to severe tropical storm status, with 10-minute maximum sustained winds of 95 km/h (60 mph).

Only July 1, the system's circulation became broad, with most of the convection located west of the center. The next day, Chataan briefly weakened to an intensity of 85 km/h (50 mph), although it began strengthening steadily on July 3, when its center passed very near Weno in Chuck State in the FSM. At 1800 UTC that night, the JTWC upgraded Chataan to a typhoon, and about 24 hours later the JMA followed suit while the storm was approaching Guam from the southeast. At about 2130 UTC on July 4, the eye of Chataan moved across northern Guam in about two hours, although the center of the eye passed north of the island.

After affecting Guam, Chataan continued toward the northwest and gradually intensified. At 0000 UTC on July 8, the typhoon reached its peak intensity of 175 km/h (110 mph ) while located near the Japanese island of Okinotorishima. The JTWC assessed that Chataan had reached its peak intensity of 240 km/h (150 mph ) about six hours earlier; on that basis, the agency classified the system as a super typhoon. On July 8, Chataan turned toward the north around the subtropical ridge while maintaining its peak winds for about 18 hours. On July 9 the typhoon turned to the northeast, and late that day it weakened to a severe tropical storm. At around 1530 UTC on July 10, Chataan made landfall on the Bōsō Peninsula in Honshu with winds of about 100 km/h (65 mph ). The storm briefly moved offshore before making a second landfall on eastern Hokkaido at 1200 UTC on July 11; this marked the first occasion of a July landfall on the island in 28 years. A few hours later, Chataan became an extratropical cyclone in the Sea of Okhotsk, where the remnants stalled before dissipating on July 13 near Sakhalin.