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:

____________________________________________

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:

 HTML tutorial HTML tutorial

Like the podcast? Support on Patreon Become a Patron!




________________________________

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.

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.
_________________________________

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.



















October 20, 2021

The Bomb Cyclone Offshore

 The next 24 hours are going to be meteorologically exciting as a powerful storm grows rapidly offshore.

And before I say more, let me make clear that the inland areas of the Northwest will NOT get a major blow from this.   Along the coast and particularly along the coast of Vancouver Island, this will be a significant event.

But this storm is remarkable for several reasons and thus is worthy of description.  And is predicted to be a bomb cyclone, in which the central pressure lowers by more than 24 hPa in 24 h. 

The latest NOAA/GFS forecast for sea level pressure at 5 AM tomorrow morning, shows a deep low off our coast, with a central pressure of 956 hPa.   A very, very deep storm for our latitudes, and lower than some category 1 and 2 hurricanes.  If this storm had been shifted a few hundred miles eastward, the damage would have been terrible.   But it will not do this:   model solutions have converged, with little chance of an inland path.


The wind forecast for 5 PM tomorrow shows gusts reaching 50-60 knots off our coast, and even stronger near the low center.

And the Seattle Windwatch wind gust forecast for 11 AM tomorrow predicts 60-80 mph just off the coast, and 30-50 mph gusts along the Washington coast and over the western Strait of Juan de Fuca.  Not a good day to head out to sea.

The most extreme coastal winds will be along the northern coast of Vancouver Island, where 60-70 mph gusts (orange colors) are predicted around 11 AM.  This is the result of a strong pressure difference coupled with the high terrain near the coast.


If this storm pans out, it will be a remarkable success for numerical weather prediction, considering the difficulty of predicting the rapid intensification of a tropical system moving northward into the midlatitudes.  

Imagine.  

Predicting the path of a storm over thousands of miles, as it switches its energy sources (from warm water and tropical moisture to horizontal temperature differences) and structure (symmetric tropic storm with fronts to a highly asymmetric storm with fronts), while predicting radical changes it is strength....and doing it all correctly.... is an extraordinary feat.

A feat of prediction we could not have done two decades ago.

And to be a little controversial for a second, some of this extraordinary technology might be of value to other communities, such as those that do epidemiological prediction.  

_____________________________________________

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 19, 2021

Saving California

 California has experienced a very dry year, with the precipitation since January 1st well below normal in most of the state, with particularly dry conditions in the northern portion where several of the big reservoirs are located. Some areas are down as much as 15-20 inches!



And not surprisingly the reservoirs are generally quite low right now,  with a number down to roughly 35-40% of normal (see below).   Not good.

Making the situation more worrisome, a La Nina is a near certainty for this winter, which generally produces drier than normal conditions over central and southern CA.

But sometimes the atmosphere does not follow persistence or the expected playbook, and at least for the next week, the northern part of the Golden State is going to be hit hard with rain.  It may be called the Sodden State.

To give you some insight into this situation, below is the latest ensemble forecast from the highly skillful European Center modeling system fortotal precipitation over the western U.S. for the next 15 days.

Wow.  Not only is BC and Washington wet, but northern CA gets as much as 12-14 inches.  That would make a huge difference, helping to refill the reservoirs.


And the UW WRF model prediction of total precipitation for the next week is also wet with huge amounts over the Sierra Nevada and northern CA.


Not satisfied?  The 46 day precipitation anomaly forecast (the difference from normal) through December 3 shows a MUCH wetter than normal autumn over northern CA.


Now if they only would stop wasting water in agriculture (like 1 gallon used PER ALMOND), the water situation might stabilize down there.

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And I know you are curious about our big storm offshore.  It is still coming to our offshore waters on Thursday.  Here is the latest forecast from the European Center for Thursday morning.  Around a 955 hPa low.  Impressive

_____________________________________________

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 17, 2021

A Superstorm of Tropical Origin Will Develop Off the Northwest Coast on Thursday

 I have been watching this storm for a while, and I am now certain enough to tell you about it.

A powerful, unusually deep storm will develop off the Northwest coast on Thursday.

A mid-latitude cyclone that began as a tropical storm (Namtheun), now over the western Pacific.

Below is the 96-hour forecast valid at 5 AM Thursday (PDT) of sea level pressure from the U.S. NOAA/GFS model.   The solid lines are isobars (lines of constant sea level pressure).

Amazing...the storm, located due west of our coast, has a central pressure is 952 hPa, which is very, very low for a mid-latitude cyclone at our latitude.  

This storm is deeper (lower pressure) than the extreme Columbus Day storm of October 12, 1962--the greatest storm to hit the Northwest in 100 years or more.


The highly skillful European Center forecast at the same time (see below) is virtually the same, providing confidence in this prediction.


The simulated satellite image near the time of greatest strength is impressive, with frontal clouds swirling into the center of the low.  At that time, an associated from is making landfall on the BC and Northwest coastline.  Big storm.


As noted earlier, this strong, mid-latitude cyclone (low-pressure center) has its origins in Tropical Storm Namtheun, which is now many thousands of miles away (see visible satellite picture yesterday.)

It is a storm undergoing extratropical transition, changing both its structure and energy sources.   From deriving its energy from the warm waters of the tropical Pacific to the horizontal temperature differences of the midlatitudes.

The meteorological version of a hybrid car.  

Let me show you its path through a series of sea level pressure forecasts by the European Center model.  I put some black arrows in to show you the low center position.

Today at 5 PM...the low center is way over in the western Pacific.

5 AM Tuesday, it has moved northward and to the east

5 PM Wednesday, it has weakened, but is still identifiable, now in the central Pacific.


And by 5 PM Wednesday it has intensified rapidly and is now off our coast.


The storm revs up at an unimaginable pace on Wednesday and Thursday morning, deepening by 48 hPa in the 24h ending 5 AM Thursday.  This makes it a superbomb storm, with the term "bomb" used for storms that deepen by 24 hPa (a unit of pressure) in 24 hr.  This storm DOUBLES that...and does most of the amplification in 12 hr.   Stunning.

Fortunately for us, the storm is predicted to head northward away from the Northwest coast and to weaken as it moves into the Gulf of Alaska.....as suggested by the forecast for Thursday evening (shown below).


What about wind speeds?  The European Center surface wind gust forecasts for Thursday morning predicts around 80 mph near the low and even higher speeds in the coastal waters off northern British Columbia.    

Trust me...this is NOT the time to take an Alaska cruise.

And this storm will produce big waves, with the forecast significant wave heights for 5 PM Thursday reaching 30-35 ft.

The relatively short period of this quickly moving and amplifying storm is helping to keep the waves down to simply huge.

Truly major midlatitude cyclones reaching our shores are often associated with tropical disturbances originating in the western Pacific.  That is true of the great Columbus Day storm.   Tropical cyclones are frequent this time of the year and the jet stream is strong enough to supply needed energy and a fast ride to the east.

And don't forget that our big heatwave in late June could be traced to a tropical cyclone moving northward, causing big downstream waves to develop after it banged into the jet stream.

_____________________________________________

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...