WPAC Tropical Weather Outlook - 6/30/25

Active tropical cyclones:

• There are no tropical cyclones.

Disturbances/invest areas:

• Invest 98W (east of Catanduanes): A broad area of low pressure located east of Catanduanes is producing a large area of widely scattered showers and thunderstorms. Despite the shower activity being limited, the system appears to have a well defined surface circulation. This system is interacting with a long-lived TUTT cell, and development is unlikely during the next day or two, but by midweek, the TUTT cell is expected to fill and environmental conditions will become much more conducive for development. A tropical depression is likely to form by Wednesday or Thursday as the system remains nearly stationary. By the end of the week, the system is forecast to begin moving northward. Interests in Okinawa should monitor the progress of this system.

  Formation chance through 48 hours: MEDIUM - 50%

  Formation chance through 7 days: HIGH - 70%

• Invest 99W (near Guam): Another area of low pressure located along the monsoon trough just west of Guam is producing disorganized showers and thunderstorms. This system is expected to merge with invest 90W located to its northeast during the next day or two and it is not expected to become a tropical cyclone.

  Formation chance through 48 hours: VERY LOW - 0%

  Formation chance through 7 days: VERY LOW - 0%

• Invest 90W (east of the Northern Mariana Islands): A third low pressure area located east of the CNMI at the very end of the active monsoon trough is producing a large area of disorganized showers and thunderstorms. This system is also interacting with an upper-level low/TUTT cell positioned over the northernmost Marianas, and upper-level winds are only marginally conducive for development. Conditions should become more favorable later this week as the system moves northwestward, and a subtropical or tropical depression is likely to form by Thursday or Friday.

  Formation chance through 48 hours: MEDIUM - 40%

  Formation chance through 7 days: HIGH - 70%

• Disturbance A (north of Palawan): Yet another low pressure area located along the monsoon trough north of Palawan is producing a large cluster of showers and thunderstorms. Upper-level winds could become conducive for some gradual development later this week as the system moves slowly and erratically northward into the South China Sea.

  Formation chance through 48 hours: VERY LOW - 0%

  Formation chance through 7 days: LOW - 30%