Typhoon Choi-wan passed east of Iwo To on Sunday. At 11:00 p.m. EDT on Sunday the center of Typhoon Choi-wan was located at latitude 25.7°N and longitude 146.4°E which put the center about 325 miles (525 km) east of Iwo To. Choi-wan was moving toward the northwest at 12 m.p.h. (19 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 916 mb.
Typhoon Choi-wan intensified to the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale on Sunday. An eyewall replacement cycle appeared to be starting in Typhoon Choi-wan. A circular eye with a diameter of 20 miles (32 km) was at the center of Choi-wan’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. The inner end of a rainband wrapped around the existing eye and eyewall. A larger outer eyewall appeared to be forming around the existing eye and eyewall. Bands of showers and thunderstorms were revolving around the core of Typhoon Choi-wan. Storms near the core of Choi-wan generated upper level divergence that pumped mass away from the typhoon. The removal of mass caused the surface pressure to decrease.
The circulation around Typhoon Choi-wan was large. Winds to typhoon force extended out 80 miles (130 km) from the center of Choi-wan’s circulation. Winds to tropical storm force extended out 355 miles (575 km) from the center of Typhoon Choi-wan.
The Hurricane Intensity Index (HII) for Typhoon Choi-wan is 31.6. The Hurricane Size Index (HSI) is 27.4 and the Hurricane Wind Intensity Size Index (HWISI) is 59.0. Typhoon Choi-wan is similar in intensity to Hurricane Laura when Laura hit Southwest Louisiana in 2020. Typhoon Choi-wan is much larger than Hurricane Laura was.
Typhoon Choi-wan will move through an environment that will be favorable for intensification during the next 24 hours. Choi-wan will move over water where the Sea Surface Temperatures are near 28°C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Even though Typhoon Choi-wan will move through a favorable environment, Choi-wan is likely to weaken during the next 24 hours because of the eyewall replacement cycle.
Typhoon Choi-wan will move around the western end of a high pressure system that is over the Western North Pacific Ocean. The high pressure system will steer Choi-wan toward the north during the next 24 hours. On its anticipated track, the center of Typhoon Choi-wan will pass east of Japan during the next few days.
Elsewhere over the Western North Pacific Ocean, Tropical Storm Koguma formed north of Kwajalein and former Hurricane Nolo moved west of the International Date Line. Nolo is now designated as Typhoon Nolo because it is over the Western North Pacific Ocean.
At 11:00 p.m. EDT on Sunday the center of Tropical Storm Koguma was located at latitude 10.8°N and longitude 168.0°E which put the center about 125 miles (200 km) north of Kwajalein. Koguma was moving toward the northeast at 11 m.p.h. (17 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 1002 mb.
At 11:00 p.m. EDT on Sunday the center of Typhoon Nolo was located at latitude 25.0°N and longitude 178.6°W which put the center about 315 miles (510 km) southwest of Midway Island. Nolo was moving toward the west-northwest at 18 m.p.h. (30 km/h). The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h). The minimum surface pressure was 955 mb.