Bombogenesis adds to shipping woes in the NE Pacific

Amidst the global supply chain crisis, the ports of the western United States and Canada are also feeling the impact of the current weather pattern over the NE Pacific. A recent storm reached hurricane force over the Gulf of Alaska setting new records that have not been experienced over the past several decades. This post will detail the atmospheric conditions which led to the development of this historic system and its impacts on the maritime industry. 

The conditions over the Gulf of Alaska were a perfect blend to provide rapid cyclogenesis. A strong blocking high over mainland Canada had kept a complex and broad low parked over the Gulf of Alaska through the week leading up to this record breaking explosive  cyclogenesis on 24th October.  Explosive cyclogenesis is also known as ‘bomb cyclone’ or ‘bombogenesis’ and happens when a system deepens by more than 24 millibars in 24 hours. The GOES-17 image for this system on 24 October is shown at Figure 1.

Figure 1. GOES-17 image on 24 October 2021

A very strong jet streak shown in Figure 2 with winds in excess of 170kts in its core, then acted to progress a series of storms rapidly east across the North Pacific through the week prior, only to come to a sudden halt as they approached the western edge of the blocking high extending southwest over British Columbia, Washington, Oregon, and Northern California. The exit of the jet streak remained positioned over the Gulf of Alaska, resulting in strong divergence of air in the upper levels of the atmosphere and supported rapid storm development in the region. 

Figure 2. GFS 250mb showing strong jetstreak over Gulf of Alaska for 22/18Z 23 october. Source TropicalTidbits

The storm which made landfall along the Washington coast Sunday 24th October began as a developing low off the coast of Japan on the morning of 20th October. By 18Z on Friday 22nd October the system began to interact with the aforementioned broad low pressure system over the Gulf of Alaska, becoming an open wave low that was further accelerated eastward in the tight gradient south of the system and subsequently underwent bomb cyclogenesis on the 23rd October.  Figure 3 shows the NWS forecast for 24/12Z issued 13/1742Z. The NWS recorded that the pressure bottomed out around 942.5 millibars at 1750Z on October 24th, as the lowest pressure ever recorded off the Washington coast with hurricane force winds.

Figure 3.  NWS Surface Forecast for 24/1200Z issued 23/1742Z October. Souce: NOAA NCEP

The Astoria Canyon Buoy, some 230nm W of the Columbia River estuary, recorded a peak of 10.7 metre wave heights and maintained very rough seas (greater than 6 meters)  for a period of 34 hours between 24/1756Z and 26th/0426Z.  Figure 4 shows how extensive the dangerous sea conditions were over the region. The Columbia river pilot service was suspended for the duration of this storm, stopping all inbound and outbound traffic from the Columbia river with similar actions up and down the west coast, as well as ships being  diverted to avoid the dangerous conditions. 

Figure 4. GFS Significant Wave heights for 24/00Z . Source Tropicaltidbits

Impacts from this historic system will be added to the current shipping crisis and felt down the supply chain.  However, the story does not stop here as global models begin to forecast an eerily similar repeat weather pattern for the Gulf of Alaska this coming week as extratropical cyclone Typhoon Malou is expected to move quickly E over the North Pacific and then become near stationary over the Gulf of Alaska on 3rd November. 

Be sure to tune in for future blogs. 

Stay safe and stay connected.

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