Tropical Storm Surigae developed southwest of Yap on Tuesday. At 5:00 p.m. EDT on Tuesday the center of Tropical Storm Surigae was located at latitude 8.2°N and longitude 137.1°E which put it about 35 miles (55 km) west-southwest of Ngulu. Serigae was moving toward the northwest at 4 m.p.h. (6 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1000 mb.
Former Tropical Depression 02W strengthened southwest of Yap on Tuesday and the Japan Meteorological Agency designated the system as Tropical Storm Surigae. The circulation around Tropical Storm Surigae exhibited more organization on satellite images. Thunderstorms developed near the center of circulation. More thunderstorms also formed in bands revolving around the center of Surigae. Storms near the center of circulation began to generate upper level divergence that pumped mass away from the tropical storm. Winds to tropical storm force extended out 50 miles (80 km) from the center.
Tropical Storm Surigae will be in an environment favorable for intensification during the next several days. Surigae will be over water where the Sea Surface Temperatures will be near 30°C. It will be under the axis of an upper level ridge over the Western North Pacific Ocean. The upper level winds are weak near the axis of the ridge and there will be little vertical wind shear. The circulation around Tropical Storm Surigae will continue to get better organized. Surigae will intensify and it could strengthen to a typhoon within 48 hours.
Tropical Storm Surigae will move around the southwestern part of a subtropical high pressure system over the Western North Pacific Ocean during the next few days. The high will steer Surigae toward the northwest during the next few days. On its anticipated track Tropical Storm Surigae will pass north of Palau. Bands on the eastern side of Tropical Storm Surigae could bring gusty winds and locally heavy rain to Yap. Persistent heavy rain could cause flash floods. Surigae could be east of the Philippines by late this week.
Powerful Typhoon Yutu churned toward northern Luzon on Friday. At 5:00 p.m. EDT on Friday the center of Typhoon Yutu was located at latitude 17.7°N and longitude 135.9°E which put it about 900 miles (1450 km) east of Cape Engano, Philippines. Yutu was moving toward the west-northwest at 17 m.p.h. (28 km/h). The maximum sustained wind speed was 160 m.p.h. (260 km/h) and there were wind gusts to 195 m.p.h. (315 km/h). The minimum surface pressure was 920 mb.
After completing an eyewall replacement cycle Typhoon Yutu strengthened again on Friday. Yutu is once again the equivalent of a Category 5 hurricane on the Saffir-Simpson Scale. The eyewall replacement cycle also caused an increase in the size of Typhoon Yutu’s circulation. Winds to typhoon force extend out about 80 miles (130 km) from the center of circulation. Winds to tropical storm force extend out about 260 miles (420 km) from the center. The Hurricane Intensity Index (HII) is 35.0. The Hurricane Size Index (HSI) is 28.9 and the Hurricane Wind Intensity Size Index (HWISI) is 63.9.
Typhoon Yutu has a large, very well organized circulation and it will remain in an environment capable of supporting a powerful typhoon for several more days. Yutu will move over water where the Sea Surface Temperature is near 31°C. It will move through an area where the upper level winds are weak and there will be little vertical wind shear. Typhoon Yutu could strengthen a little more during the next 12 to 24 hours. At some point another rainband is likely to wrap around the existing eye and eyewall, and another eyewall replacement cycle could occur. If there is another eyewall replacement cycle, then Yutu would weaken, at least temporarily.
Typhoon Yutu will move south of a ridge of high pressure over the Western North Pacific Ocean. The ridge will steer Yutu in a generally westward direction. On its anticipated track Typhoon Yutu could reach northern Luzon in about four days. Yutu is very likely to be a strong typhoon when it approaches Luzon.
Typhoon Koppu intensified rapidly during the past 12 hours and it is making landfall near Baler in northern Luzon as the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale. At 11:00 a.m. EDT on Saturday the center of Typhoon Koppu was located at latitude 16.0°N and longitude 122.9°E which put it about 170 miles (275 km) east-northeast of Manila, Philippines. Koppu was moving toward the west-northwest at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 150 m.p.h. (240 km/h) and there were wind gusts to 185 m.p.h. (295 km/h). The minimum surface pressure was 918 mb. Typhoon Koppu has a Hurricane Intensity Index (HII) of 31.6, a Hurricane Size Index (HSI) of 17.5 and a Hurricane Wind Intensity Size Index (HWISI) of 49.1, which means it is capable of producing regional significant wind damage. In addition the slow movement of Koppu means it will produce very heavy rainfall which will create the potential for serious flooding and landslides.
Koppu will continue to move toward the west-northwest for another 12 to 24 hours. Then it will reach the western end of the subtropical ridge that has been steering it and start to move toward the north. Although Typhoon Koppu will weaken as it moves across northern Luzon, it will be over that area for 36 to 48 hours. Koppu has the potential to cause widespread damage due to winds, floods and landslides.