Typhoon Halong intensified to the equivalent of a major hurricane over the Western North Pacific Ocean south of Japan on Tuesday morning.  At 11:00 a.m. EDT on Tuesday the center of Typhoon Halong was located at latitude 28.4°N and longitude 137.2°E which put the center about 490 miles (785 km) south-southwest of Tokyo, Japan.  Halong was moving toward the northwest at 8 m.p.h. (13 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 942 mb.

Typhoon Halong intensified to the equivalent of a Category 4 hurricane on the Saffir-Simpson Scale on Tuesday morning.  A circular eye with a diameter of 40 miles (65 km) was at the center of Halong’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 Halong.  Storms near the core of Halong generated upper level divergence that pumped mass away from the typhoon in all directions.  The removal of large amounts of mass caused the surface pressure to decrease rapidly.

The circulation around Typhoon Halong was relatively small.  Winds to typhoon force extended out 30 miles (50 km) from the center of Halong’s circulation.  Winds to tropical storm force extended out 140 miles (225 km) from the center of Typhoon Halong.

The Hurricane Intensity Index (HII) for Typhoon Halong was 25.1.  The Hurricane Size Index (HSI) was 10.2 and the Hurricane Wind Intensity Size Index (HWISI) was 35.3.  Typhoon Halong was similar in size and intensity to Hurricane Harvey when Harvey hit Texas in 2017.

Typhoon Halong will move through an environment that is favorable for intensification during the next 24 hours.  Halong will move over water where the Sea Surface Temperatures are near 29°C.  It will move under the middle of an upper level ridge that is south of Japan.  The upper level winds are weak near the middle of the upper level ridge and there will be little vertical wind shear.  Typhoon Halong will intensify during the next 24 hours.

Typhoon Halong will move around the western end of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Halong toward the north during the next 24 hours.  On its anticipated track, Typhoon Halong will move closer to Honshu.