WPAC Tropical Weather Outlook: 7/9/25

Enormous monsoon gyre in the western half of the basin consists of Invests 91W and 92W, both of which have some development potential, while another disturbance could form southwest of Guam

Author

Will Weaver
July 09, 2025

Active tropical cyclones:

  • There are no tropical cyclones.

Disturbances/invest areas:

  • Invest 91W (between Okinawa and Iwo Jima): A mid- to upper-level low pressure area with a weak surface circulation is located in the northern Philippine Sea roughly halfway between Okinawa and Iwo Jima. Shower activity associated with this system has increased somewhat during the past 24 hours. Upper-level winds are only marginally conducive for development, but a tropical depression could form by Friday or Saturday as the system begins to move northeastward.

    Formation chance through 48 hours: LOW - 30%

    Formation chance through 7 days: MEDIUM - 50%

  • Invest 92W (northeast of Taiwan): An area of low pressure is located along the periphery of a broad monsoon gyre spanning the East China Sea and the northwestern Philippine Sea, partially including the remnants of Typhoon Danas. Shower activity associated with this system remains disorganized. Although upper-level winds are not particularly conducive for development, this system could consolidate into a tropical depression by this weekend as it meanders in the East China Sea, then turns toward the northeast.

    Formation chance through 48 hours: LOW - 10%

    Formation chance through 7 days: MEDIUM - 40%

  • Disturbance A (northwest of the Marianas): An area of disturbed weather located northwest of the CNMI is associated with a pair of surface troughs and an upper-level low. Only limited development of this system is likely before it moves northward and merges with Invest 91W later this week. 

    Formation chance through 48 hours: LOW - 10%

    Formation chance through 7 days: LOW - 10%

  • Disturbance B (southwest of Guam): A new area of low pressure is forecast to form in the eastern Philippine Sea southwest of Guam over the weekend. Some gradual development is possible as the system moves generally northwestward through early next week.

    Formation chance through 48 hours: VERY LOW - 0%

    Formation chance through 7 days: LOW - 30%