Typhoon Shanshan strengthened to the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale over the northern Ryukyu Islands on Tuesday.  At 5:00 p.m. EDT on Tuesday the center of Typhoon Shanshan was located at latitude 29.2°N and longitude 130.0°E which put the center about 90 miles (145 km) south-southwest of Kamiyaku, Japan.  Shanshan was moving toward the north-northwest at 5 m.p.h. (8 km/h).  The maximum sustained wind speed was 130 m.p.h. (210 km/h) and there were wind gusts to 160 m.p.h. (260 km/h).  The minimum surface pressure was 932 mb.

Typhoon Shanshan intensified to the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale on Tuesday.  A circular eye with a diameter of 30 miles (50 km) was at the center of Shanshan’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 Shanshan.  Storms near the core generated strong upper level divergence that pumped mass away from the typhoon.  The removal of mass caused the surface pressure to decrease.

The circulation around Typhoon Shanshan was symmetrical.  Winds to typhoon force extended out 30 miles (50 km) from the center of Shanshan’s circulation.  Winds to tropical storm force extended out 145 miles (230 km) from the center of Typhoon Shanshan.

The Hurricane Intensity Index (HII) for Typhoon Shanshan was 25.1.  The Hurricane Size Index (HSI) was 12.1 and the Hurricane Wind Intensity Size Index (HWISI) was 37.2.  Typhoon Shanshan was similar in size and intensity to Hurricane Harvey when Harvey hit Texas in 2017.

Typhoon Shanshan will move through an environment that will be favorable for intensification during the next 24 hours.  Shanshan will move over water where the Sea Surface Temperatures are near 29°C.  It will through a region where the upper level winds are weak and there will be little vertical wind shear.  Typhoon Shanshan could intensify during the next 24 hours.

Typhoon Shanshan will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Shanshan toward the north-northwest during the next 24 hours.  On its anticipated track, Typhoon Shanshan will toward western Kyushu.  Shanshan could approach western Kyushu in 36 hours.

Typhoon Shanshan will continue to produce strong winds and heavy rain in the northern Ryukyu Islands.  The eastern side of the eyewall of Shanshan will move near Yakushima.  Shanshan will be capable of causing severe damage.  Heavy rain is likely to cause flash floods in some locations.  Typhoon Shanshan will also cause a storm surge in the northern Ryukyu Islands where the wind blows the water toward the shore.