Typhoon Koinu approached Taiwan from east on Tuesday night. At 11:00 p.m. EDT on Tuesday the center of Typhoon Koinu was located at latitude 22.1°N and longitude 123.3°E which put it about 175 miles (280 km) east of Hengchun, Taiwan. Koinu was moving toward the west-northwest at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 115 m.p.h. (185 km/h) and there were wind gusts to 145 m.p.h. (230 km/h). The minimum surface pressure was 953 mb.

Typhoon Koinu was the equivalent of a major hurricane as it approached Taiwan on Tuesday night. A circular eye with a diameter of 30 miles (50 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 were revolving around the core of Typhoon Koinu. Storms near the core generated strong upper level divergence that pumped large quantities of mass away from the typhoon.

The size of the circulation around Typhoon Koinu increased on Tuesday. Winds to typhoon force extended out 90 miles (145 km) from the center of Koinu’s circulation. Winds to tropical storm force extended out 200 miles (320 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Koinu was 20.6. The Hurricane Size Index (HSI) was 29.2 and the Hurricane Wind Intensity Size Index (HWISI) was 49.8. Typhoon Koinu was similar in size and intensity to Hurricane Frances when Frances hit southeast Florida in 2004.

Typhoon Koinu will move through an environment favorable for intensification during the next 12 hours. Koinu 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. Typhoon Koinu is likely to intensify during the next 12 hours.

Typhoon Koinu will move around the southern part of a high pressure system over eastern Asia and the Western North Pacific Ocean. The high pressure system will steer Koinu toward the west during the next 24 hours. On its anticipated track the center Typhoon Koinu will reach the coast of southeast Taiwan in less than 24 hours. Typhoon Koinu is likely to be the equivalent of a major hurricane when it approaches Taiwan. Koinu will bring strong, gusty winds and locally heavy rain to Taiwan. Heavy rain will cause flash floods in some locations. Typhoon Koinu could also cause widespread outages of electricity.