Large Typhoon Khanun churned over the Western North Pacific Ocean west of Okinawa on Wednesday night. At 11:00 p.m. EDT on Wednesday the center of Typhoon Khanun was located at latitude 26.6°N and longitude 124.6°E which put it about 190 miles (310 km) west of Okinawa. Khanun was moving toward the west-northwest at 4 m.p.h. (6 km/h). The maximum sustained wind speed was 105 m.p.h. (1650 km/h) and there were wind gusts to 125 m.p.h. (200 km/h). The minimum surface pressure was 951 mb.

The inner end of a rainband wrapped around an existing eye and eyewall on Wednesday and concentric eyewalls formed in Typhoon Khanun. The inner eye had a diameter of 15 miles (25 km). The inner eye was surrounded by a ring of thunderstorms and the strongest winds were occurring in that ring of storms. The inner eyewall was surrounded by a large clear area called a moat. The moat was surrounded by a large outer eyewall that had a diameter of 115 miles (185 km). Bands of showers and thunderstorms were revolving around the concentric eyewalls. Storms in the concentric eyewalls generated upper level divergence that pumped mass away from the typhoon.

The size of the circulation around Typhoon Khanun increased when the concentric eyewalls formed. Winds to typhoon force extended out 115 miles (185 km) from the center of Khanun’s circulation. Winds to tropical storm force extended out 235 miles (380 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Khanun was 17.8. The Hurricane Size Index (HSI) was 37.0 and the Hurricane Wind Intensity Size Index (HWISI) was 54.8. Khanun is capable of causing extensive serious damage. Typhoon Khanun was large than Hurricane Ivan was when Ivan hit the U.S. Gulf Coast in 2004. Khanun was not quite as strong as Ivan was.

Typhoon Khanun will move through an environment that will be favorable for a strong typhoon during the next 24 hours. Khanun 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. However, Typhoon Khanun is likely to weaken during the next 24 hours, because of the concentric eyewalls. The inner eyewall is likely to weaken and the low level convergence will occur into the large, outer eyewall. Since the strongest winds are in the inner eyewall, the wind speed will decrease when the inner eyewall weakens.

Typhoon Khanun will be in an area where the steering currents are weak during the next 24 hours. On its anticipated track, Typhoon Khanun will meander west of Okinawa during the next 24 hours. Khanun is forecast to move back toward the east-northeast later this week. The center of Typhoon Khanun could pass north of Okinawa on Friday. Khanun is forecast move across the northern Ryukyu Islands in 48 hours. Typhoon Khanun will continue to produce strong, gusty winds and locally heavy rain in Okinawa and other Ryukyu Islands. Heavy rain will cause flash floods in some locations.