Tropical Depression (90W/Isang) – Tropical Cyclone Advisory #1: 0000 UTC 22 August 2025

Tropical depression forms just off the eastern coast of Luzon, expected to move inland during the next few hours.

Author

Will Weaver
August 21, 2025

…Tropical depression forms just off the eastern coast of Luzon… …Expected to move inland during the next few hours…

Himawari-9 visible satellite image (Weathernerds)

Current storm information:

  • Position: 16.0°N 122.5°E

  • Movement: W at 7 knots (10 km/h)

  • Intensity: 30 knots (55 km/h)

  • Central pressure: 1006 hPa

Trend:

  • Little change in strength is forecast during the next 24 hours.

Watches and warnings:

  • There are currently no land-based watches or warnings in effect - however, TCWS #1 will likely be issued shortly for portions of central Luzon.

Hazards affecting land:

  • The depression is expected to cause areas of moderate to heavy rain over portions of central and southern Luzon during the next 12 to 24 hours. Given that most of the rainfall is occurring west of the center, it will probably not last very long. However, storm total rainfall of up to 100 mm is possible through tonight. Heavier rainfall associated with the monsoon is possible in portions of Mindoro and the Western Visayas, with amounts up to 150 mm possible.

Discussion:

Himawari-9 infrared satellite image (Weathernerds)

With very little time to spare, the area of low pressure east of Luzon (invest 90W) developed a better defined circulation center, with discrete banding features wrapping into it from the south and west. This convection is displaying the effects of strong easterly shear associated with a strong upper-level ridge positioned to the northeast, but has persisted close enough to the center and with enough organization for the system to be designated a tropical depression. The initial intensity is set to 30 kts, based on consensus Dvorak fixes of T2.0 from PGTW, KNES, and RJTD. It should be noted that the depression has a sprawling area of convective banding extending to the south and west of the center, reaching as far south as northeastern Palawan as the outflow feeds into a weak monsoon trough to the south.

The depression is about to make landfall during the next few hours. Given its sheared appearance, no significant change in strength is expected before then. Although TD 90W will be passing over some rough terrain, its circulation is expected to survive passage over land and emerge back over water late tonight. Once over water, the depression should encounter a more favorable environment, and it will likely become a tropical storm on Saturday as it moves almost due west across the South China Sea. 90W should gradually accelerate as the ridge to the north strengthens, and it will likely move inland over Vietnam by Tuesday. Rapid weakening and dissipation should follow by Wednesday as the system quickly moves inland.

Forecast positions and maximum winds

  • 00 hrs: 16.0°N 122.5°E – 30 kts

  • 12 hrs: 17.2°N 119.6°E – 30 kts

  • 24 hrs: 17.2°N 117.6°E – 35 kts

  • 48 hrs: 17.2°N 112.5°E – 45 kts

  • 72 hrs: 17.6°N 108.7°E – 55 kts

  • 96 hrs: 18.3°N 105.4°E – 35 kts inland

  • 120 hrs: 19.0°N 102.1°E – 25 kts inland

JMA forecast map

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