MIMIC Total Precipitable Water fields, above, (archived here), show the motion of Typhoon Bolaven as it evolved from a strong typhoon west of 150^o E Longitude on 10 October to a potent extratropical cyclone approaching 150^oW Longitude on 16 October 2023, at which later time a long filament of tropical moisture continued to accompany the system. True Color imagery from the CSPP Geosphere site, below, shows the elongated system with the cold front stretching to the west-southwest.

MIMIC TPW fields over the eastern Pacific at 1800 UTC on 16 October, below, show two different moist airstream; one is affecting the Pacific Northwest of the USA (and southwestern Canada) at 1800 UTC. The moisture with the remains of Bolaven is approaching from the west. The GFS model initialized on 1200 UTC on 16 October suggests the next 72 hours will be wet along Coastal British Columbia with widespread rainfalls of 4-6″ (link, from this site) .

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GOES-18 Air Mass RGB images, from 0600 UTC on 14 October to 2100 UTC on 16 October (courtesy Scott Bachmeier, CIMSS) [click to play animated GIF | MP4]

GOES-18 Air Mass RGB images from 14-16 October (above) showed the period during which Typhoon Bolaven made its extratropical transition to a Hurricane Force Low on 14 October and then to an expansive Storm Force Low on 16 October (surface analyses from OPC). The darker shades of red to orange in the RGB imagery depicted a Potential Vorticity anomaly associated with this strong storm system. 

At 2100 UTC on 16 October, a cross section of AK-NAM40 model Potential Vorticity and Wind Speed along Line J-J’ (below) highlighted a well-defined tropopause fold, descending below the core of a 130-knot jet stream (which was situated along the southern periphery of the storm).

Cross section along Line J-J’, showing AK-NAM40 model Potential Vorticity and Wind Speed [click to enlarge]

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