Typhoon Koinu moved southeast of Hong Kong on Friday night. At 11:00 p.m. EDT on Friday the center of Typhoon Koinu was located at latitude 21.1°N and longitude 115.3°E which put it about 115 miles (185 km) southeast of Hong Kong. Koinu was moving toward the west-southwest at 4 m.p.h. (6 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 952 mb.

Typhoon Koinu intensified back to the equivalent of a major hurricane over the South China Sea southeast of Hong Kong on Friday. A circular eye with a diameter of 12 miles (19 km) was at the center of Koinu’s circulation. The eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. Bands of showers and thunderstorms revolved around the core of Typhoon Koinu. Storms near the core generated upper level divergence that pumped mass away from the typhoon.

Wins to typhoon force extended out 40 miles (65 km) from the center of Typhoon Koinu. Winds to tropical storm force extended out 285 miles (460 km) in the northeast quadrant of Koinu’s circulation. Winds to tropical storm force extended out 130 miles (210 km) in the other parts of Typhoon Koinu. The Hurricane Intensity Index (HII) for Typhoon Koinu was 22.1. The Hurricane Size Index (HSI) was 14.9 and the Hurricane Wind Intensity Size Index (HWISI) was 37.0. Typhoon Koinu was similar in size and intensity to Hurricane Harvey when Harvey hit Texas in 2017.

Typhoon Koinu will move through an environment somewhat favorable for a strong typhoon during the next 24 hours. Koinu will move over water where the Sea Surface Temperatures are near 28°C. It will move under the southern part of an upper level ridge over China. The ridge will produce easterly winds that will blow toward the top of Koinu’s circulation. Those winds will cause some vertical wind shear. The wind shear will inhibit intensification. The circulation around the northern side of Typhoon Koinu could draw in some drier air from China. Typhoon Koinu could maintain its intensity during the next 24 hours if the drier air does not reach the inner core of the circulation. Koinu is likely to weaken if the drier penetrates to the core of the circulation.

Typhoon Koinu will move will move around the southern part of a high pressure system over eastern Asia. The high pressure system will steer Koinu slowly toward the west-southwest during the next 24 hours. On its anticipated track the center Typhoon Koinu will move south of Hong Kong on Saturday.

Elsewhere over the Western North Pacific Ocean, Tropical Depression 15W formed east-southeast of Guam. At 11:00 p.m. EDT on Friday the center of Tropical Depression 15W was located at latitude 9.9°N and longitude 154.2°E which put it about 700 miles (1130 km) east-southeast of Guam. The tropical depression was moving toward the west-northwest at 13 m.p.h. (21 km/h). The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h). The minimum surface pressure was 1003 mb.