Typhoon Halong strengthened to the equivalent of a major hurricane northeast of the Northern Marianas on Monday. At 4:00 p.m. EST on Monday the center of Typhoon Halong was located at latitude 18.9°N and longitude 152.1°E which put it about 390 miles (630 km) south of Minami Tori Shima, Japan. Halong was moving toward the northwest at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 120 m.p.h. (195 km/h) and there were wind gusts to 150 m.p.h. (240 km/h). The minimum surface pressure was 952 mb.
Typhoon Halong continued to strengthen on Monday and it reached the equivalent of a major hurricane. A small, well formed circular eye was evident on infrared satellite images. The eye was surrounded by a ring of strong 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 were generating strong upper level divergence which was pumping mass away from the typhoon.
The circulation around Typhoon Halong increased in size on Monday. Winds to typhoon force extended out 45 miles (75 km) from the center of circulation. Winds to tropical storm force extended out 160 miles (260 km) from the center. The Hurricane intensity Index (HII) for Typhoon Halong was 22.0. The Hurricane Size Index (HSI) was 14.3 and the Hurricane Wind Intensity Size Index was 36.3. Halong was capable of causing major damage.
Typhoon Halong will remain in an environment favorable for intensification for another 24 hours. Halong will move over water where the Sea Surface Temperature is near 29°C. It will move under the northwestern portion of an upper level ridge where the winds are weaker and there will be little vertical wind shear. An upper level trough southwest of Japan will approach Typhoon Halong in 24 hours. The trough will produce stronger southwesterly winds which will cause more vertical wind shear. Halong will start to weaken when the wind shear increases.
Typhoon Halong will move around the western end of a subtropical high pressure system over the Western North Pacific Ocean during the next 36 to 48 hours. The ridge will steer Halong toward the north-northwest. Halong will move toward the northeast later this week after if moves around the western end of the high pressure system. On its anticipated track Typhoon Halong could approach Minami Tori Shima in less than 72 hours.