Tropical Update

Invest 91W continues to slowly consolidate near the Marianas and could become a cyclone in the next 24 hours. The Joint Typhoon Warning Center has issued a Tropical Cyclone Formation Alert indicating a HIGH chance of development in the next 24 hours. JMA, on the other hand, is already classifying 91W as a Tropical Depression and expects it to become a Tropical Storm in the next 24 hours.

IR Image from NOAA

Invest 91W was last located approximately 450km SSW of Iwo To or about 800km north northwest of Guam. It is currently moving northwestward at 10kph. Earlier satellite images indicate winds of around 30 to 40kph near the center, with stronger 40 to 60kph winds located east of the disturbance. A TUTT cell to the northwest is providing good outflow to the LPA. Sea surface temperatures in that area are very warm, ranging from 29 to 31C. Wind shear is mostly weak to moderate (10-20kt) although it increases dramatically west of the system.

Computer models are in better agreement as to 91W's future track. The consensus is now taking the said system on a northwestward course towards the Ryukyu Islands in Japan. Most of the models are also showing a weak tropical storm at best. For now, the system will be slow to move due to the presence of conflicting steering patterns. However, by tomorrow, we expect 91W to slowly accelerate eventually reaching the Japanese Islands as early as Tuesday night/Wednesday morning.

We'll have another update tomorrow.
________________________________________________
Issued (10 UTC) 6pm PhT 071512