Typhoon Sinlaku battered Tinian and Saipan on Tuesday. At 11:00 a.m. EDT on Tuesday the center of Typhoon Sinlaku was located at latitude 15.1°N and longitude 145.7°E which put the center about 20 miles (30 km) south of Saipan. Sinlaku was moving toward the northwest at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 145 m.p.h. (235 km/h) and there were wind gusts to 175 m.p.h. (285 km/h). The minimum surface pressure was 930 mb.
Typhoon Warnings are in effect for Rota, Tinian, Saipan, Pagan, Alamagan, and Agrihan.
A Tropical Storm Warning is in effect for Guam.
A Typhoon Watch is also in effect for Guam.
A weather station at the international airport in Saipan reported a sustained wind speed of 82 m.p.h. (132 km) and a wind gust of 130 m.p.h. (210 km/h) as the eyewall of Typhoon Sinlaku passed over it.
Typhoon Sinlaku began an eyewall replacement cycle just before it reached Tinian and Saipan. A larger, outer eyewall formed around the smaller, original eyewall. The low level convergence began to be intercepted by the outer eyewall and the original inner eyewall began to weaken. The weakening of the inner eyewall caused the strongest winds in Typhoon Sinlaku to diminish very gradually.
The remnant of the original inner eyewall was still visible on satellite and radar images of Typhoon Sinlaku. The larger outer eyewall appeared to be becoming the predominant feature in the core of Sinlaku’s circulation. Bands of showers and thunderstorms were revolving around the core of Typhoon Sinlaku. Storms near the core of Sinlaku generated upper level divergence that pumped mass away from the typhoon. The removal of mass in the upper levels of the atmosphere was less than the strong convergence of mass in the lower levels. So, the surface pressure was increasing gradually.
The circulation around Typhoon Sinlaku was large. Winds to typhoon force extended out 75 miles (120 km) from the center of Sinlaku’s circulation. Winds to tropical storm force extended out 265 miles (425 km) from the center of Typhoon Sinlaku.
The Hurricane Intensity Index (HII) for Typhoon Sinlaku is 29.9. The Hurricane Size Index (HSI) is 27.4 and the Hurricane Wind Intensity Size Index (HWISI) is 57.3. Typhoon Sinlaku is similar in size and intensity to Hurricane Helene when Helene hit Florida in 2024.
Typhoon Sinlaku started to move more slowly as it began the eyewall replacement cycle. The slower movement was prolonging the period destructive wind and rain in Tinian and Saipan. Sinlaku was capable of causing severe damage. Prolonged heavy rain is likely to cause flash floods.
Flood Watches are in effect for Guam, Rota, Tinian, and Saipan.
Typhoon Sinlaku could cause a storm surge of up to 13 feet (4 meters).
Typhoon Sinlaku will move around the western part of a high pressure system that is over the Western North Pacific Ocean. The high pressure system will steer Sinlaku toward the north-northwest during the next 24 hours. On its anticipated track, the center of Typhoon Sinlaku will move very slowly away from Tinian and Saipan. Sinlaku will be west of the Marianas on Wednesday.
Typhoon Sinlaku will move into an environment that will be marginally favorable for a strong typhoon during the next 24 hours. Sinlaku will move over water where the Sea Surface Temperatures are near 28°C. It will move under the middle of an upper level ridge that is over the Western North Pacific Ocean. The upper level winds are weak near the middle of the ridge and there will be little vertical wind shear. Typhoon Sinlaku will move into a region where the air is drier. The drier air is likely to inhibit the development of thunderstorms in the northern and western parts of Sinlaku’s circulation. Typhoon Sinlaku is likely to continue to weaken gradually during the next 24 hours because of the eyewall replacement cycle and the drier air.