December 25, 2020

Solstice Wind Storm in Leavenworth, Washington

 While western Washington residents were amazed by the extreme weather of December 21, including snow, heavy rain, flooding, record temperatures and more, another extreme event struck the eastern slopes of the Cascades near Leavenworth, resulting in very strong winds, downed trees, and power outages for over a thousand customers.  The picture below provides a sample of the bedlam.

Picture courtesy of Heather Murphy and Don Schaechtel 

The cause of the eastern Washington destruction? The same as in the west. A very strong cold front.

The eastern slopes of the Cascades have been the scene of extraordinarily powerful downslope windstorms on several occasions as strong westerly (from the west) flow accelerated down into the Columbia Basin.  A famous event occurred in 1974 when a number of train cars were derailed and fell into the Columbia River near Vantage.


On Monday evening, strong winds from the west followed the passage of the powerful cold front, with a large pressure difference (gradient) developing over the Cascades (see surface weather map at sea level pressure, winds, and temperature).


A map of observed maximum wind gusts on Monday around Leavenworth (red oval) on Monday shows a 52 mph gust just east of town, 79 mph at Alpental Summit, and 100 mph at Mission Ridge ski area.  Clearly, the observing network is not dense enough to spotlight all the strong wind areas.


The Mission Ridge Summit (6730 ft) winds are shown in more detail below, with the shading indicating the range of winds at any time.  100 mph is evident, as is the extreme gustiness of the wind speeds.  Strongest winds were from the northwest (270 indicates winds from from the west).


The UW high resolution model  maximum gust forecast (in knots) for 10 PM Monday shows how structured and localized the strong winds were. Powerful winds  (blue, orange and red colors).west of Leavenworth where the terrain descends downward quickly.  Since the graphics shown are from an 18-h forecast, it was clear that some warning could have been given.


You will also  notice a large area of strong winds near Vantage (blue colors) and mega winds around the summit of Mount Rainier.  

The complex wind patterns around the Northwest make the meteorology challenging but our high-resolution models give us a powerful tool for providing localized warnings.

9 comments:

  1. Any snow possibilities on the horizon...or even just a few snow flakes...

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  2. A little bit of that sneaked over the Pass to Gold Bar, where it was 61 degrees F. around 1 p.m., a sudden gust that knocked out power, and then by 6:30 p.m., it was 33 degrees and starting to snow. Okaaaay...

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  3. I'm with Gus Bus. When the early winter forecasts stated much colder and wetter than normal, my snow-loving inner child was very happy. We ended up getting around 2 inches of snow at Lake Goodwin, NW of Marysville on the 21st. Is this our "one and done?" Newer forecast trends show above normal temps for Jan/Feb with possible below average temps for March. What happened to the strong La NiƱa influence?

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  4. I find it hard to digest this blog when the high resolution UW model predicts something, but Dr. Mass complains it was not used. The referenced forecast models are an incredibly difficult product to use. This is because the data available is only in low quality images (i.e. no labels), but even more importantly, the underlying data is not publicly available - even though it is developed using public funding. Access requires an expensive license. If the data were publicly available, it could be incorporated into weather forecasting apps, etc... If UW staff are not going to develop usable, consumer facing products out of it, why not allow the public to?

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    Replies
    1. Beth.. I asm sorry you find the UW model graphics difficult to understand and use. There are many thousands of graphics available for outsider users to view. The raw graphics is very, very large we do not have the resources to support providing this data to the outside community. The modeling is supported by the NW modeling consortium, whick pays for the computers used to run the model. Only supporting members are given access to the raw grids....cliff

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  5. I live in Leavenworth, and was taking the dog out for his evening piddle when I heard the storm coming. It was coming over Icicle ridge, and hadn't reached the valley floor. It sounded like a huge waterfall was about to land on us.

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  6. We were staying at the Sleeping Lady Resort, a couple of miles up the Icicle River from Leavenworth. Looking at the windspeed map, almost exactly where the 52 MPH reading is indicated. It was just howling! We lost power somewhere around 10 or 11. Came back on the next morning at 4.

    I wonder if the Icicle Canyon, being very deep and narrow, doesn't accelerate the wind speeds.

    It died back down as fast as it came up. I was grateful that we were able to drive home the next morning. Chelan PUD and the local road crews had everything moving by 9 when we departed. They don't dilly-dally over there.

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  7. Hi Cliff & readers...a wind speed observation yesterday courtesy of FlightAware website. I watched an airliner at cruise fly over our home east of Redmond yesterday and checked it out of FlightAware. It was ANA flight 12, Tokyo - Narita to Chicago O'Hare. FL350, ground speed 600 mph. I looked at its flight track, and about an hour east of Japan in the Pacific, FL 300, it had a sharp spike in ground speed that peaked at 795 mph. Assuming a set cruise speed of Mach 0.85 (@ FL 300 = 576 mph) that suggests a tailwind of 222 mph. Better a tail wind than a head wind. Best wishes.

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  8. I was working out of state this winter when this storm happened. I got reports of damage from my house sitters the next morning (we live above the house pictured with the damage). My Davis weather system recorded winds at 0 up until the it suddenly went to 67, 83, and 36 in each half hour interval that the equipment makes a record. During that same time it also recorded gusts of 138, 137, and 137.

    The only problem is that the system time and dates are offset and I don't know why or when exactly that happened. I lost data too as the sitter downloaded and because of the date/time offset older data was apparently overwritten. I called the NWS in Spokane and they won't accept my report of 138mph gusts because no other station nearby got even that close.

    But the Schaechtels and the folks in my house say they believe the gusts were that high. All seem to think the super localized event strongly resembled a twister.

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