Page Text: This blog discusses current weather, weather prediction, climate issues, and current events
October 21, 2021
The Strongest Storm in Northwest History Could Reach Our Coastal Waters On Sunday
(Note: I will have a new blog and podcast by 1 PM...waiting on new model guidance for the storm)
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On Sunday, the most powerful storm in Northwest history, with the lowest central pressure ever observed in our region, will approach our coast.
There are still uncertainties with its track...as well as its impacts on the region. But there is now little doubt that an extraordinary event is in store, as unusual as the June heatwave. This blog will fill you in on the details.
The Current Offshore Storm
The offshore storm today was one of the strongest on record, with the sea level pressure in its center dropping to around 951 hPa-- in the range of a category three hurricane.
I have studied such intense midlatitude cyclones (low-pressure areas) for years, and the lowest central pressure in the historical record off our coast is 950 hPa.
The satellite image this morning shows an impressive storm, with clouds swirling into the low center. And a front is about to make landfall on our coast, resulting in substantial precipitation over land.
As predicted, this storm produced extreme winds along the coast of Vancouver Island, including 100 mph at Solander Island on the north coast (see a map of winds at 9 AM, gusts are in red). Only 40-50 mph gusts along the Washington coast.
The Monster Storm on Sunday
What is predicted for Sunday is a different animal....a far more powerful and dangerous one. An unprecedented animal. And an animal whose moves are still somewhat uncertain, unlike the last storm, which proved to be highly predictable and stable.
Below is the forecast sea-level pressure on Sunday at 11 AM by the U.S. GFS model.
I could not believe my eyes when I saw this. 942 hPa central pressure. Never has a storm with such low pressure moved this far south to the waters immediately offshore of the Pacific Northwest. Not even the 1962 Columbus Day Storm (which was only 955 hPa)
The European Center model, the best in the world, has a very similar solution, but with slightly higher pressure (944 hPa). Just stunning.
Further confidence is provided by the ensemble forecasts, in which each of these models is run many times, starting with slightly different conditions. The solution is robust.
We are going to have a record-breaking monster storm off our coast...the most intense in the historical record.
But the winds on land will be controlled by the storm's path and changes in storm strength over time. Both the U.S. and European models have this system weakening as it approaches land, but the tracks are different.
The GFS model is much more threatening, with the low center moving across the northwest tip of the Olympic Peninsula. Here is the forecast for Monday at 5 PM from the UW model, which is driven by the U.S. GFS model. A 973 hPa low making landfall, with large pressure differences along the coast.
The result would be a significant windstorm for the region, with strong winds, gusting to 60-70 mph along the coast and 30-40 mph gusts in the interior. The European Center prediction takes the storm further north (see below), greatly reducing impacts on the Northwest.
As a general rule, I would bet on the European Center model, which suggests that we won't get a major blow in the interior. But with such a strong storm and so much uncertainty, my colleagues and I will have to watch developments carefully. By tomorrow, we should have a reliable track for the storm, so keep tuned.
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