Post-Tropical Cyclone Halong (28W) – Tropical Cyclone Advisory #13 (FINAL): 1200 UTC 10 October 2025

…Halong becomes a post-tropical cyclone and is on the express train to the Arctic Ocean… …This is the last advisory, but you don’t want to miss it!…

Current storm information:

• Position: 34.6°N 162.3°E

• Movement: E at 25 knots (45 km/h)

• Intensity: 65 knots (120 km/h) [Category 1]

• Central pressure: 978 hPa

Trend:

• The post-tropical cyclone is forecast to strengthen during the next 24 hours.

Discussion:

Satellite imagery and cyclone phase diagrams indicate that Halong has become a post-tropical cyclone. Although there is still some deep convection occurring fairly close to the center, this convection is gradually becoming decoupled from an increasingly elongated surface circulation by extremely strong (70 to 80 kts) westerly shear. The circulation center is also becoming embedded in very cool and very dry air, and well-defined warm and cold fronts are attached to it, with the cold front extending almost to where Tropical Storm Nakri is. The intensity remains 65 kts, based on a recent RCM-2 SAR pass that indicated a large area of 60 to 65 kt winds occurring to the north and northeast of the center. This is slightly ahead of a Miller-Lander extratropical transition technique fix of XT3.5 (55 kts) from PGTW.

Halong is about to embark upon a journey that not many former tropical cyclones take. Although Halong will weaken in the short term due to strong shear and interaction with a very deep extratropical low in the far western Bering Sea, the southwesterly flow associated with that low will cause Halong to rocket toward the northeast. In fact, by Sunday it will have passed over the Aleutian Islands and entered the Bering Sea itself. Interaction with a large pool of cold air in the Bering Sea will cause post-tropical Halong to explosively intensify as it continues moving northeastward, and it will likely re-attain hurricane-force winds later on Sunday as it passes west of Nome. By Monday, post-tropical Halong should begin a final weakening trend before making landfall southeast of Point Hope in northwestern Alaska, then emerging over the Arctic Ocean near Utqiagvik on Monday evening. 

Although post-tropical Halong should then become embedded within the polar vortex, almost all of the available model guidance suggests that Halong will remain a distinct entity through the end of a full 5-day forecast period, by which time Halong will be moving over the islands of Canada’s Northwest Territories, less than 500 nautical miles from the North Pole. The GFS, in fact, brings Halong to nearly 80°N! Most of the guidance finally has Halong becoming absorbed within the vortex by next weekend. 

This is the last advisory on Halong. For additional information on this system, refer to products from the U.S. National Weather Service, Environment Canada, or your local weather office. And yes, that last forecast point is 108.5°W longitude - the same longitude as Billings, Montana in the United States!

Forecast positions and maximum winds

• 000 hrs: 34.6°N 162.3°E – 65 kts Post-tropical/extratropical

• 012 hrs: 35.7°N 167.2°E – 60 kts Post-tropical/extratropical

• 024 hrs: 42.5°N 179.5°E – 60 kts Post-tropical/extratropical

• 048 hrs: 57.5°N 173.0°W – 65 kts Post-tropical/extratropical

• 072 hrs: 68.2°N 162.5°W – 50 kts Post-tropical/extratropical inland over Alaska

• 096 hrs: 74.3°N 131.5°W – 40 kts Post-tropical/extratropical over Arctic Ocean

• 120 hrs: 78.7°N 108.5°W – 35 kts Post-tropical/extratropical