Typhoon #Halong (28W) – Tropical Cyclone Advisory #9: 1200 UTC 8 October 2025

Category 4 Halong producing tropical storm conditions in the Izu Islands. Heavy surf and life-threatening rip current risk continues for much of southern Japan.

Author

Will Weaver
October 08, 2025

…Category 4 Halong producing tropical storm conditions in the Izu Islands… …Heavy surf and life-threatening rip current risk continues for much of southern Japan…

Himawari-9 infrared satellite image (Weathernerds)

Current storm information:

  • Position: 31.4°N 138.5°E

  • Movement: NE at 11 knots (20 km/h)

  • Intensity: 120 knots (220 km/h) [Category 4]

  • Central pressure: 940 hPa

Trend:

  • Gradual weakening is forecast during the next 24 hours.

Watches and warnings:

  • There are no coastal watches or warnings in effect.

Hazards affecting land:

  • Halong is currently producing tropical storm conditions over the Izu Islands, and it is also likely to produce heavy surf, life-threatening rip currents, and coastal flooding along the southern and eastern coast of Honshu through Friday. For additional information, refer to products from your local weather office.

  • Interests in the Aleutian Islands and mainland Alaska should monitor the progress of Halong. Halong’s post-tropical remnants could produce storm- to hurricane-force winds and heavy rain or snow over portions of western Alaska early next week. For additional information, refer to products from the U.S. National Weather Service.

Discussion:

METOP-B MMS 89GHz microwave satellite image, showing a rather lopsided system

Halong appears to be undergoing an eyewall replacement cycle. This eyewall replacement cycle happens to be occurring just as Halong has begun to exit the extremely favorable environment it had been located in, as the system has taken on a sheared appearance. The central dense overcast has become lopsided mainly to the east of the center, and the eye has become less distinct on satellite imagery. Microwave satellite imagery and JMA radar data indicate that the inner eyewall has mostly eroded away, leaving behind a much larger eye structure, although the western eyewall appears to be hanging on for dear life. CIMSS shear data indicates that southwesterly shear has increased as Halong moves out from under the upper-level ridge it had been situated under while making its recurve, and the effective shear has increased to around 20 kts. The intensity remains 120 kts, although this could be generous as it is ahead of consensus Dvorak fixes of T6.0 and ADT, AiDT, and D-PRINT estimates ranging from 105 to 115 kts.

The forecast is generally unchanged from the previous one since the models are in fairly strong agreement. Halong is currently in the process of being captured by the mid-latitude westerlies, and the typhoon is expected to accelerate toward the east-northeast during the next couple of days. As it does, Halong should interact with a strong baroclinic zone to its north, causing it to transition into a powerful post-tropical cyclone by Friday evening. After becoming post-tropical, Halong is expected to explosively intensify as it interacts with a pool of bitterly cold Siberian air to its northwest, and Halong is expected to be a large and powerful extratropical cyclone in the northern Bering Sea by the end of the forecast period. The remnants of Halong will likely dissipate in the Arctic Ocean just after the forecast period ends.

Forecast positions and maximum winds

  • 000 hrs: 31.4°N 138.5°E – 120 kts

  • 012 hrs: 33.0°N 140.7°E – 115 kts

  • 024 hrs: 33.8°N 145.6°E – 105 kts

  • 048 hrs: 34.0°N 160.0°E – 90 kts Post-tropical/extratropical

  • 072 hrs: 40.0°N 173.6°E – 70 kts Post-tropical/extratropical

  • 096 hrs: 55.5°N 175.5°W – 70 kts Post-tropical/extratropical

  • 120 hrs: 64.1°N 173.5°W – 70 kts Post-tropical/extratropical

JMA forecast map. The extratropical phase is omitted.