Former Tropical Storm Halong strengthened to a typhoon west of the Ogasawara Islands south of Japan on Sunday night.  At 5:00 a.m. EDT on Monday the center of Typhoon Halong was located at latitude 25.9°N and longitude 140.5°E which put the center about 665 miles (1075 km) south of Tokyo, Japan.  Halong was moving toward the west at 7 m.p.h. (11 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 977 mb.

Former Tropical Storm Halong strengthened to a typhoon on Sunday night.  A small circular eye formed at the center of Halong’s circulation.  The eye was surrounded by a broken ring of thunderstorms and the strongest winds were occurring in that ring of storms.  Thunderstorms were also occurring in bands in the eastern side of Typhoon Halong.  Bands in the western side of Halong’s circulation consisted primarily of showers and lower clouds.  Storms near the center of Halong generated upper level divergence that pumped mass away from the typhoon.  The removal of mass caused the surface pressure to decrease.

The distribution of wind speeds in Typhoon Halong was relatively symmetrical.  Winds to typhoon force extended out 25 miles (40 km) from the center of Halong’s circulation.  Winds to tropical storm force extended out 115 miles (185 km) from the center of Typhoon Halong.

Typhoon Halong will move through an environment that is mostly 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.  However, Halong will move into a region of drier air.  The drier air will inhibit the formation of thunderstorms in the western part of Halong’s circulation.  Typhoon Halong is likely to intensify during the next 24 hours if the drier air does not get pulled into the core of Halong.

Typhoon Halong will move around the southwestern part of a high pressure system over the Western North Pacific Ocean.  The high pressure system will steer Halong toward the northwest during the next 24 hours.  On its anticipated track, Typhoon Halong will move a little closer to Japan.

Elsewhere, the center of Tropical Storm Matmo moved over northeastern Vietnam.  At 5:00 a.m. EDT on Monday the center of Tropical Storm Matmo was located at latitude 22.4°N and longitude 106.2°E which put the center about 25 miles (40 km) east of Na Phac, Vietnam.  Matmo was moving toward the west-northwest at 13 m.p.h. (21 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.