WPAC Tropical Weather Outlook - 9/15/25

Active tropical cyclones:

• There are no tropical cyclones.

Disturbances/invest areas:

• Invest 98W (central South China Sea): An area of low pressure located in the central South China Sea about halfway between Luzon and Vietnam is showing some signs of organization, although its associated shower activity is limited and scatterometer data indicates the low is only producing winds of 15 to 20 knots. Although environmental conditions are conducive for development, this system only has about a day or so to become a short-lived tropical depression before it moves inland over northern Vietnam.

  Formation chance through 48 hours: LOW - 30% 🟡

  Formation chance through 7 days: LOW - 30% 🟡

• Invest 99W (east of Catanduanes): A broad area of low pressure is located east of Catanduanes and is producing a large area of disorganized showers and thunderstorms. Environmental conditions are conducive for development, and a tropical depression or tropical storm is likely to form by Wednesday as the system moves northwestward off the eastern coast of Luzon, then turns west-northwestward and enters the Luzon Strait. Interests in northern Luzon, the Batanes and Babuyan Islands, and southern Taiwan should monitor the progress of this system. The system could produce areas of heavy rainfall in those areas between Tuesday and Friday. For additional information, refer to products from your local weather office. 

  Formation chance through 48 hours: MEDIUM - 50% 🟠

  Formation chance through 7 days: HIGH - 80% 🔴

• Disturbance A (northwest of Guam): Another area of low pressure located in the far eastern Philippine Sea northwest of Guam is producing clusters of disorganized showers and thunderstorms. Upper-level winds are conducive for development, and this system will likely become a tropical depression or tropical storm by the end of the week as it moves northwestward, then turns westward in the northern Philippine Sea. Interests in Okinawa and the Yaeyama Islands should monitor the progress of this system.

  Formation chance through 48 hours: LOW - 30% 🟡

  Formation chance through 7 days: HIGH - 70% 🔴