Sunday, November 13, 2011

High Winds Hit the Eastern Cascade Slopes

The big weather action today was on the eastern slopes of the Cascades, where winds were gusting nearly to 100 mph at some locations-- 96 mph at Mission Ridge.  Here are the winds at 7 pm and 7 AM, with the red numbers giving you the gusts:

7 AM
7 PM

The winds were very variable and intermittent...some places got hit by strong gusts for a while and later experienced light winds.  Here are the winds today at a high (6730 ft) east-slope location--Mission Ridge:

Some mighty good windchill up there! In contrast, winds at Ellensburg were only gusting into the 30s (knots)

Now to understand these winds one must begin by noting we have had a VERY powerful jetstream over the Pacific that has headed right into us from the northwest.
Here is the upper level chart at 300 hPa (around 31,000 ft) at 4 PM Sunday..   Some winds are well over 150 knots, with some reaching 190 kt (219 mph!!).  Don't try to fly to Asia...it will take forever.
Winds indicate by dashed lines and barbs.
These strong winds have interacted with the Cascades.  First, air approaching the mountains rise, cool, becomes more dense and causes a windward high pressure area.  As air descends, it warms, becomes less dense and produces a lee trough.   Air accelerates as it goes from high to low pressure.  And such a pressure distribution was evident across the Cascades today (see map below at 10 AM).  Here is the proof.

And the interaction of the strong flow with the mountains can produce mountain waves that can bring down the momentum from aloft and enhance wind speed.   Here is an east-west vertical cross section across the Cascade today and you can see this effect (shading indicates wind speeds--dark red is strong, and air flow tends to follow the solid lines):

Lets take a look at the wind gust prediction at the surface (really 10 meters) from the high resolution WRF model today at 4 PM.  The first is from the 4-km grid spacing domain and the second is from our ultra-resolution 4/3 km domain.  Lots of gusts over 50 kts in the high-resolution domain.


 Hate to say it...but there will be plenty more of this over the next few days.

6 comments:

smokejumper said...

I posted a comment last night about wild winds, but this afternoon they were insane. I recorded a gust of 58mph. Not record breaking, but i'd estimate today was a 1 in 3-4 year windstorm.

But our wind is so variable. Its localized, due to the diverse terrain etc. And leeward troughs. I don't understand them. The vertical cross section map you posted is accurate. Hurricane one spot, relatively calm another.

And the winds will die down soon. In fact, I think we might see our first snow of the year Wed. morning due to some cool air damming and a SE gradiant. Not much, maybe an inch.

Ferdi said...

A very strong squall came through from the northwest this morning. Strong winds and heavy rain. It left a dusting of snow on the top of Orcas Island's Mt.Constitution. Sinclair Island lies just south of the Strait of Georgia and I can see the Canadian Coast Mts. from my place - a long fetch over water. So the wind can get a real head of steam when the pressure gradient is right.

Ashford98304 said...

BTW, with your new graphics presentation my IMac will only show the thumbnails; clicking on the picture just skips to the next picture.

windlover said...

Cliff ~ Saturday night Scott Sistek posted on facebook that the long range models were showing a wind storm for the 27th. Have you seen anything hinting at that and if so, how likely do you think it will be that it actually comes to pass? Sorry...I know long range forcasts are extremely "iffy" but I love a good wind storm...!!!

Charlie Phillips said...

Windlover - the 27th is a long ways out, and you can't pin down an individual storm that far out on the models. However, the models seem to be trending towards a stormy pattern later next week, and the last week of November is typically the stormiest time of the year! I'm hoping for a windstorm too. In the meantime, we could get pretty blustery on Wednesday.

blackcap said...

It seems to be cooling off rapidly tonight. With there being a chance of showers by tomorrow morning, what would you say is the chance of a "timing is everything" bout of snow showers tomorrow morning?

See scenario 5 at:
http://www.komonews.com/weather/blogs/scott/117085073.html

I remember this happening in mid/late November in the mid 90s one year.