Luzon Strait: Tropical Storm Usagi tracking northwestward to the southwest of Taiwan as of Nov. 15 /update 6

Typhoon Usagi (known in the Philippines as Ofel) is tracking northwestward in the Luzon Strait Nov. 15, having passed over far northeastern Luzon and past the northern island regions of the Philippines Nov. 14. As of 17:00 CST, the system's center of circulation was approximately 485 km (301 miles) south-southwest of Taipei, Taiwan.

Forecast models indicate that the system will weaken slightly as it turns to track northeastward toward southern Taiwan through early Nov. 16, before making landfall over Kaoshiung City near the border with Pingtung County during the morning Nov. 16. After landfall Usagi is expected to weaken into a tropical depression as it tracks northeastward across southern Taiwan and into eastern Taiwan through early Nov. 17. The system is expected to dissipate as it turns northward near the eastern coast of Taiwan Nov. 17. Some uncertainty remains in the track and intensity forecast, and changes could occur in the coming days.

As of Nov. 15, the Taiwan Central Weather Administration has issued a sea and land typhoon warning covering southern areas of Taiwan and southern coastal waters. Yellow heavy rain advisories (the lowest level on a four-tier scale) are in place over mountainous areas of Pingtung County, the Hengchun Peninsula, Taitung County, and Lanyu and Ludao Islands. Strong wind advisories are also in place for the Hengchun Peninsula.

The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) is maintaining a tropical cyclone bulletin for Usago (Ofel) advising that the system will continue to bring strong winds and rough seas to far northern regions. A Tropical Cyclone Warning Signal 1 remains in place for Batanes Province.

Authorities in the Philippines preemptively evacuated tens of thousands of residents in hazardous areas across the Cordillera Administrative, Ilocos, and Cagayan Valley regions ahead of the arrival of Usagi. Classes have been suspended at schools in parts of Cagayan Valley and Cordillera Administrative regions. Initial damage assessments have reported some flooding and associated damage to buildings and bridges in parts of Cagayan Province following the passing of the storm, but no casualties have been confirmed as of Nov. 15.

Much of the northern and central Philippines are still recovering from previous storms, including Tropical Storm Trami (named Kristine in the Philippines), which made landfall in Divilacan Town, Isabela Province, at around 00:30 Oct. 24; Tropical Storm Kong-rey (named Leon in the Philippines), which made a close approach to northeastern Luzon Oct. 30-31; Tropical Storm Yinxing (named Marce in the Philippines), which passed over the north coast of Luzon Nov. 7; and Typhoon Toraji (named Nika in the Philippines), which made landfall near Dilasag in Aurora Province early Nov. 11. The succession of tropical systems has caused widespread flooding, damage, and associated disruptions across the region. Tens of thousands of people remain evacuated following damage caused by the storms, with parts of Cagayan Province among the worst affected areas. Further severe weather associated with Typhoon Usagi will likely lead to more disruptions and hamper recovery efforts.

Sustained heavy rainfall could trigger flooding in low-lying areas and those with easily overwhelmed drainage systems. If weather conditions prove hazardous, localized evacuations, flash flooding, and landslides are possible.

Inclement weather could trigger localized business, transport, and utility disruptions, rendering some bridges or roadways impassable. Flight disruptions at regional airports and temporary port closures are also possible. Stagnant pools of water during and after flooding increase insect- and waterborne diseases, such as dengue fever, cholera, and malaria. Exposure to raw sewage and other hazardous materials mixed with floodwaters poses a serious health threat.