The eye of Typhoon Muifa passed directly over Ishigakijima on Sunday night. A weather station on Ishigakijima measured a surface pressure of 968.3 mb. At 11:00 p.m. EDT on Sunday the center of Typhoon Muifa was located at latitude 24.4°N and longitude 124.2°E which put it about 5 miles (10 km) east of Ishigaki, Japan. Muifa was moving toward the north-northwest at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 100 m.p.h. (160 km/h) and there were wind gusts to 120 m.p.h. (195 km/h). The minimum surface pressure was 967 mb.

Typhoon Muifa developed two concentric eyewalls and began an eyewall replacement cycle as it slowly approached Ishigakijima on Sunday. The inner end of rainband wrapped around the existing eye and eyewall and a larger outer eyewall surrounded them. Low level convergence became concentrated in the outer eyewall and the thunderstorms in the inner eyewall weakened. The remnants of the inner eyewall were visible on satellite images as a ring of showers and lower clouds. The outer eyewall had a diameter of 60 miles (95 km). The strongest winds were occurring in the outer eyewall. Bands of showers and thunderstorms were revolving around the core of Typhoon Muifa. Storms near the core generated upper level divergence that pumped mass away from the typhoon.

The eyewall replacement cycle caused Typhoon Muifa to weaken as it approached Ishigakijima. Winds to typhoon force extended out 35 miles (55 km) from the center of Typhoon Muifa. Winds to tropical storm force extended out 120 miles (195 km) from the center of circulation. The Hurricane Intensity Index (HII) for Typhoon Muifa was 16.5. The Hurricane Size Index (HSI) was 13.9 and the Hurricane Wind Intensity Size Index (HWISI) was 30.4. Typhoon Muifa was capable causing regional serious damage.

Typhoon Muifa will move through an environment favorable for intensification during the next 24 hours. Muifa will move over water where the Sea Surface Temperatures are near 30˚C. It will move through a region where the upper level winds are weak and there will be little vertical wind shear. Typhoon Muifa could intensify during the next 24 hours after the inner eyewall completely dissipates. Since Typhoon Muifa will move slowly, its winds could mix cooler water up to the surface of the ocean. Cooler water would limit potential intensification.

Typhoon Muifa will move around the western part of a high pressure system over the Western North Pacific Ocean. The high pressure system will steer Muifa slowly toward the north-northwest during the next 36 hours. Typhoon Muifa will continue to produce strong winds and locally heavy rain in the southern Ryukyu Islands during the next 24 hours. The strongest winds and heaviest rain are likely to affect Ishigakijima. Gusty winds and locally heavy rain could also affect Miyakojima. On its anticipated track Typhoon Muifa could approach the east coast of China near Shanghai in 60 hours.

Elsewhere over the Western North Pacific Ocean, Tropical Storm Merbok was slowly strengthening west-northwest of Wake Island. At 11:00 p.m. EDT on Sunday the center of Tropical Storm Merbok was located at latitude 21.6°N and longitude 161.6°E which put it about 365 miles (595 km) west-northwest of Wake Island. Merbok was moving toward the east-northeast at 6 m.p.h. (10 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 1000 mb.