A well defined low level circulation developed in an area of thunderstorms east of the Philippines on Thursday and the system was designated as Tropical Storm Linfa (10W).  At 5:00 p.m. EDT on Thursday the center of Tropical Storm Linfa was located at latitude 16.3°N and longitude 127.6°E which put it about 470 miles (760 km) east-northeast of Manila, Philippines.  Linfa was moving toward the northwest at 7 m.p.h. (11 km/h).  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were wind gusts to 60 m.p.h. (95 km/h).  The minimum surface pressure was 993 mb.

Linfa developed over water where the Sea Surface Temperature (SST) is near 30°C,  There is sufficient energy in the upper ocean to support intensification.  An upper level ridge centered northwest of Linfa is producing northeasterly winds over the top of the circulation and most of the thunderstorms are occurring west of the center.  The vertical wind shear is modest and some upper level divergence is present, especially over the western half of the circulation.  The vertical wind shear is expected to remain moderate and Linfa could intensify during the next several days.  If the upper level winds weaken, then a period of more rapid intensification is possible.

Linfa is being steered by a subtropical ridge located to the east of the tropical storm.  The ridge is expected to steer it toward the northwest in the short term.  As Linfa reaches the western end of the ridge it is expected to be steered more toward the north.  The timing of the turn toward the north will be important because it will determine if Linfa moves over the northern Philippines or moves northeast of that area.  The timing on the turn to the north will also determine the potential risk for Taiwan.  Another factor that could complicated the track forecast is a potential interaction with Typhoon Chan-hom which is abut 1500 miles (2400 km) east-southeast of Linfa.