Former Tropical Storm Halong strengthened into a typhoon east of the Northern Marianas on Sunday.  At 4:00 p.m. EDT on Sunday the center of Typhoon Halong was located at latitude 17.0°N and longitude 153.3°E which put it about 520 miles (840 km) east-northeast of Saipan.  Halong was moving toward the northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h).  The minimum surface pressure was 979 mb.

The circulation around former Tropical Storm Halong exhibited much better organization on Sunday.  An eye with a diameter of approximately 12 miles (19 km) formed at the center of Halong.  A ring of strong thunderstorms surrounded the eye and the strongest winds were occurring in that ring of storms.  Bands of showers and thunderstorms were revolving around the core of Typhoon Halong.  The strongest rainbands were north and east of the center of circulation.  Bands in the western half of Halong consisted primarily of showers and lower clouds.  Typhoon Halong may have been pulling sinking, drier air into the western half of the circulation, which may be why the bands were weaker in that part of the typhoon.  Storms around the core of Halong were generating strong upper level divergence which was pumping mass away from the typhoon.  Winds to typhoon force extended out 10 miles (15 km) from the center of circulation.  Winds to tropical storm force extended out 175 miles (280 km) from the center.

Typhoon Halong will move through an environment favorable for intensification during the next 36 to 48 hours.  Halong will move over water where the Sea Surface Temperature is near 29°C.  It will move under the western part of an upper level ridge where the winds are weak.  So, there will not be a lot of vertical wind shear.  Typhoon Halong will continue to intensify and it could strengthen into the equivalent of a major hurricane.

Typhoon Halong will move around the western end of a ridge of high pressure over the Western North Pacific Ocean.  The ridge will steer Halong toward the northwest during the next 24 hours.  After that time Typhoon Halong will move more toward the north while it moves around the western end of the ridge.  Halong will move northeastward after it moves around the end of the ridge.  On its anticipated track Typhoon Halong is forecast to remain northeast of the Northern Marianas.  Halong is expected to pass between Iwo To and Wake Island later next week.