Post-Tropical Cyclone Bailu (13W) – Tropical Cyclone Advisory #7: 1500 UTC 4 August 2025

…Bailu rapidly becoming extratropical… …This is the last advisory…

Current storm information:

• Position: 37.6°N 154.8°E

• Movement: E at 17 knots (30 km/h)

• Intensity: 35 knots (65 km/h)

• Central pressure: 998 hPa

Trend:

• The post-tropical cyclone should gradually weaken during the next couple of days.

Discussion:

Extratropical transition is rapidly finishing up with Bailu, as the system has completely decoupled in the face of strong westerly shear and interaction with a frontal boundary extending from Post-Tropical Cyclone Krosa. The surface circulation is fully exposed and sharply elongated with the nearest convection racing away to the east along a warm front. The wind field has also expanded greatly to the south of the center. Cyclone phase diagrams show Bailu rapidly losing its warm core, and it is likely to be fully extratropical within the next few hours, so it is now a post-tropical cyclone. The winds remain 35 kts, although this could be generous as recent HYSAT and Oceansat-3 scatterometer data failed to find any winds stronger than 30 kts.

Post-tropical Bailu should follow Krosa across the cold waters of the northern Pacific. Bailu will likely not have the same amount of baroclinic forcing available to it as Krosa did, and so the cyclone will likely weaken during the next couple of days. Assuming the circulation survives, there is the potential for some restrengthening as an extratropical low later this week as the system passes south of the Alaska Peninsula.

This is the last advisory on Bailu.

Forecast positions and maximum winds

• 00 hrs: 37.6°N 154.8°E – 35 kts

• 12 hrs: 38.0°N 157.6°E – 30 kts Post-tropical/extratropical

• 24 hrs: 39.4°N 160.4°E – 25 kts Post-tropical/extratropical

• 48 hrs: 42.6°N 166.6°E – 25 kts Post-tropical/extratropical

• 72 hrs: 47.7°N 176.7°E – 30 kts Post-tropical/extratropical

• 96 hrs: 45.4°N 167.0°W – 35 kts Post-tropical/extratropical

• 120 hrs: 49.2°N 157.3°W – 40 kts Post-tropical/extratropical