Tropical Depression 20W (#Jacinto) – Tropical Cyclone Advisory #1: 1200 UTC 28 August 2025

Tropical Depression 20W forms in the central South China Sea.

Author

Will Weaver
August 28, 2025

…Tropical Depression 20W forms in the central South China Sea…

Himawari-9 infrared satellite image (Weathernerds)

Current storm information:

  • Position: 15.0°N 115.5°E

  • Movement: W at 3 knots (5 km/h)

  • Intensity: 30 knots (55 km/h)

  • Central pressure: 1001 hPa

Trend:

  • Some slow strengthening is possible during the next 24 hours, and the depression could become a tropical storm on Friday.

Watches and warnings:

  • There are no land-based watches or warnings in effect.

Hazards affecting land:

  • TD 20W is likely to bring areas of heavy rainfall to portions of Hainan Island and Vietnam beginning late Friday night and continuing through the weekend. Many areas that already saw heavy flooding rainfall from Typhoon Kajiki could see additional rain and flooding. For additional information, refer to products from your local weather office.

Discussion:

Although it is not particularly well organized from a convective structure standpoint, conventional satellite and scatterometer data indicates that the area of low pressure that moved off the western coast of Luzon yesterday has developed a well-defined surface circulation with a broad area of 25 to 30 kt winds primarily to the west of the center. The convection is not particularly well organized, consisting of an almost linear cluster of thunderstorms to the west of the center, with some more discrete bands located south of the center along the monsoon trough. The banding does not yet seem to be wrapping into the center due to some easterly shear that is disrupting the system. Nonetheless, there is enough organization here for the system to be considered a tropical depression, and the system is now Tropical Depression 20W with winds of 30 kts.

TD 20W is embedded in the same steering regime that was in place over the South China Sea when Typhoon Kajiki moved through the region - a strong mid-level ridge to the north and a broad monsoonal circulation to the south. Because of this, there is fairly strong agreement among the models regarding the track forecast. TD 20W should move generally west-northwestward during the next couple of days, passing south of Hainan Island on Friday and making landfall in north central Vietnam on Saturday. The environment is not expected to be particularly favorable due to moderate easterly shear, and only some slow strengthening appears likely before 20W moves inland over Vietnam. Although none of the models indicate it, it is possible 20W could become a tropical storm before landfall. After landfall, 20W should rapidly weaken and dissipate over northern Laos by Sunday.

Forecast positions and maximum winds

  • 00 hrs: 15.0°N 115.5°E – 30 kts

  • 12 hrs: 16.1°N 113.3°E – 35 kts

  • 24 hrs: 16.9°N 111.3°E – 35 kts

  • 48 hrs: 17.7°N 106.3°E – 30 kts inland

  • 72 hrs: Dissipated

JTWC forecast map

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