WPAC Tropical Weather Outlook - 7/31/25

Active tropical cyclones:

• Tropical Depression Co-May (11W), located inland northwest of Shanghai, China. Refer to tropical cyclone advisories.

• Severe Tropical Storm Krosa (12W), located southeast of the Izu Islands. Refer to tropical cyclone advisories.

• Tropical Storm Iona (01C), located in the Central Pacific well to the southwest of the Hawaiian Islands. Iona is forecast to cross over the International Date Line and enter the Western Pacific basin late Friday night or early Saturday morning. Tropical cyclone advisories will begin at that time.

• Tropical Depression (93W): A minor tropical depression, 996 hPa, is located south of Minamidaitojima. Estimated maximum winds are 25 knots. This system does not yet meet warning criteria. The large monsoon gyre that had dominated much of the Western Pacific for the past couple of weeks has consolidated into a broad monsoon depression-like system with a large, sprawling circulation and clusters of convection flaring mainly to the south and west of the center. Environmental conditions appear to be favorable for this system to briefly reach warning criteria in the next day or two as it moves east-northeastward. By late Sunday, strong upper-level winds and colder SSTs from Krosa's large cold wake will likely end the system's development chances, and 93W will likely be absorbed by Krosa by midweek.

Disturbances/invest areas:

• Disturbance A (far east-southeast of Guam): An area of low pressure is forecast to develop along the ITCZ well to the east-southeast of Guam over the weekend. Upper-level winds could be favorable for some gradual development as the system moves west-northwestward through early next week. By Tuesday, stronger upper-level winds will likely become much less favorable for development.

  Formation chance through 7 days: VERY LOW - 0% ⚫

  Formation chance through 7 days: LOW - 30% 🟡