Lan Strengthens to a Typhoon East of the Philippines

Tropical Storm Lan strengthened east of the Philippines on Tuesday and the Japan Meteorological Agency designated it a typhoon.  At 5:00 p.m. EDT on Tuesday the center of Typhoon Lan was located at latitude 11.2°N and longitude 132.4°E which put it about 515 miles (830 km) east of the Philippines.  Lan was moving toward the north-northeast at 5 m.p.h. (8 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. (150 km/h).  The minimum surface pressure was 976 mb.

The circulation of Typhoon Lan became much more well organized on Tuesday.  Several long rainbands developed in the circulation and other smaller bands formed in the periphery of the typhoon.  The circulation of Typhoon Lan was circular and symmetrical.  Thunderstorms near the core of Lan began to generate strong upper level divergence which was pumping mass away from the typhoon in all directions.  The upper level divergence allowed the surface pressure to decrease and the wind speed to increase.  Lan is a large typhoon.  Winds to tropical storm force extend out about 230 miles (370 km) from the center of circulation.

Typhoon Lan will move through an environment favorable for intensification.  Lan will move over water where the Sea Surface Temperature is near 30°C.  Typhoon Lan will move through an area where the upper level winds will be weak and there will be little vertical wind shear during the next several days.  Typhoon Lan will continue to strengthen and there could be a period of rapid intensification after a well formed eye develops at the center of circulation.

Typhoon Lan was in an area where the steering currents were weak and it moved little on Tuesday.  An upper level ridge north of Lan blocked the typhoon from moving northward.  A weakness is forecast to develop in the ridge and the models are forecasting that Typhoon Lan will move northward during the rest of this week.  On its anticipated track Typhoon Lan will remain east of the Philippines.  Lan could be southeast of Okinawa in three or four days.