October 23, 2021

The Storm's Future is Now Known

The models have converged to a consistent solution, the storm is beginning to "bomb", and I can now provide a forecast with some confidence.

This will be the strongest Northwest storm on record, but its strength will collapse as it approaches the coast of Vancouver Island.  More quickly than any storm in my experience.

And there will be strong winds over land, but not from the south, but from the east, as air is pulled westward by the immense, powerful storm offshore.

Let me begin by showing you the latest water vapor satellite image over the eastern Pacific (below), with the dark areas indicating dry conditions.

This is a very potent storm, with massive clouds and extreme darkening, which indicates strong sinking behind the low center (you can see the moisture curling up).  Such sinking is a sign of vigor.

Both the American (GFS) and European Center (ECMWF) models indicate very rapid intensification over the next 24h, with the storm catching down to around 943 hPa (see below for 8 AM Sunday).  This is a "bomb" cyclone, with the pressure dropping more than 24 hPa in 24 hours.




There has never been a storm this strong in the nearshore waters of our region.  

The closest was 950 hPA in 1981.

Both U.S. and European modeling systems predict massive swell/waves approaching the West Coast from this monster storm, reaching 30 feet on Sunday evening!


Both modeling systems indicated that the storm will very rapidly weaken on Monday, making landfall on Vancouver Island with a central pressure around 985 hPa (see US model forecast below) at 11 PM Monday.


I don't think I have seen so rapid a collapse of a storm over water.

But what will happen overland?   Will there be some strong winds?
The answer is yes.

Let me show you.  The three stages to this unusual event.

Stage 1:  An intense low offshore and a large east-west pressure difference over the region

At 8 AM Sunday a huge, deep low center will be due west of the Columbia River outfall.  The lines on the map are isobars, lines of constant sea level pressure.  A very large pressure difference is over us, with lowered pressure to the west.   In the presence of terrain, such a pressure gradient will produce very large easterly (from the east) winds in terrain gaps, and strong winds offshore.



Below are the predicted wind gusts at 11 AM on Sunday (in knots).  Strong easterly gusts (to roughly 55 knots) in the eastern Strait of Juan de Fuca as the air in the Strait accelerates to the west, and winds will accelerate down the western slopes of the Cascades, with powerful gusts from Enumclaw to North Bend.  Strong southeasterly winds offshore.


Stage 2. A Still Powerful Storm Moves Towards Land

Here is the sea-level pressure forecast at 8 PM Sunday.  Just wow. An absolutely intense pressure difference over the coastal waters of Oregon and Washington.  Very strong winds.


The predicted wind gusts at this time will be substantial along the coast, some reaching 60 knots (roughly 70 mph).  Strong winds over the volcanic peaks and over portions of NW Washington.


Stage 3:  The Weakened Low Moves North of western Washington

With the (weakened) low center northwest of western WA, there will be a substantial north-south pressure difference over Puget Sound and the Strait of Georgia (1 AM Tuesday is shown).  That means WIND.

Winds will be strong, southerly, and gusty over the inland waters of Puget Sound, with gusts accelerating to 30-40 mph, especially near the water.


And don't forget the precipitation.   California getting hit hard, with up to 8-10 inches through Tuesday morning (see forecast below).  And there is going to be significant snow in the North Cascades and British Columbia this week.


Time to stop.....enough weather for a day!

My Podcast Has More Background Information on the Big Storms of the Northwest:

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The Second Edition of My Northwest Weather Book is Now Available!

My new book is greatly improved and expanded over the first edition, with new chapters on the meteorology of Northwest wildfires and the weather of British Columbia.  A completely revamped chapter on the effects of global warming on our region.  And it has been brought up to date with recent weather events and the imagery is improved greatly.
 

Where can you get it?

Local bookstores, such as the University of Washington bookstore.  The UW Bookstore has just received several dozen copies.

Or secure a copy from the publisher:  UW Press.

Or Third Place Books in Lake Forest Park or Seattle.

And yes, there are online sellers like Amazon and Barnes and Noble.


October 22, 2021

Update on the Strongest Coastal Cyclone in Northwest History and an Introduction to Pacific Cyclones. All in my New Podcast

 My new podcast is out (see below) and in it I describe the hurricane-force storms that can hit Northwest and provide an update on the extraordinary Sunday/Monday event.

And I have to admit something:  meteorologists are not exactly sure where the big storm will make landfall.

However, the formation of an unprecedented storm is nearly a sure thing, with the very latest forecasts of sea level pressure for Sunday morning from both the U.S. and European models predicteing the strongest Northwest storm in history with pressures below 945 hPa (see below).  Just crazy.  Equivalent to a category three hurricane.

European Model forecast of sea level pressure for 5 AM Sunday

The American model forecast at the same time.

The strong winds and vast size of the storm will send large swell and wind-driven waves onto our coast, with some getting to 30 ft or more. Be careful if you go wave watching.

Wave forecast for Sunday night

In the podcast, I talk about the disagreement between the models on where this monster storm will go, and how it will weaken over time.  I will blog about this issue on Saturday....so keep tuned.

You can listen to the podcast below or through your favorite podcast server.



Some major podcast servers:

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Like the podcast? Support on Patreon Become a Patron!




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An Important Message for Seattle Voters

_____________________________________________

The Second Edition of My Northwest Weather Book is Now Available!

My new book is greatly improved and expanded over the first edition, with new chapters on the meteorology of Northwest wildfires and the weather of British Columbia.  A completely revamped chapter on the effects of global warming on our region.  And it has been brought up to date with recent weather events and the imagery is improved greatly.
 

Where can you get it?

Local bookstores, such as the University of Washington bookstore.  The UW Bookstore has just received several dozen copies.

Or secure a copy from the publisher:  UW Press.

Or Third Place Books in Lake Forest Park or Seattle.

And yes, there are online sellers like Amazon and Barnes and Noble.

The Storm's Future is Now Known

The models have converged to a consistent solution, the storm is beginning to "bomb", and I can now provide a forecast with some c...