November 13, 2017

Wind Storm Update

The first...and lesser act...of today's wind event took place this morning, the passage of an occluded front associated with the offshore low.  But the main act is still in the cards, and folks should be prepared.

The infrared satellite image at 6 AM shows the swirl of clouds around the low center, located southeast of Vancouver Island.  The occluded front is indicated by the roughly north-south band of cloud over the Cascades at that time.

Heavy rain accompanied the occluded front (see radar at 2 AM), and after its passage winds surged.

The maximum winds during the last 24 hr (ending 6 AM), which pretty much happened during the past 6 hours, are impressive: several over 40 mph in the central Puget Sound, with some on the Kitsap Peninsula reaching 50-60 mph.  Even stronger winds on the coast.

 Power outages have already occurred over Seattle
 And Puget Sound Energy has about 25,000 customers blacked out, including large areas over the Kitsap.

The winds above Seattle-Tacoma Airport show the movement of strong winds aloft, some of which have reached the surface in gusts.  This chart shows sustained winds from the surface to 10,000 ft (700 hPa pressure in this figure), with time increasing to the right (in UTC, 13/12 is 4 AM this morning).  The solid triangles indicate 50 knot sustained winds.  Strong winds came in aloft overnight, and intensified with the occluded front.  Temperatures area cooling as well (think snow in the mountains).

We are now in the break before the main act.   You will even notice the rain has backed off and there will be sun breaks. Absolutely typical.  We must wait until late morning/early afternoon when the low approaches and the winds will increase again, probably exceeding what we experienced last night.

The UW has developed the Seattle WindWatch site (sponsored by Seattle City Light) to assist City Light in preparing for and managing wind outages.  One of its capabilities is to present the latest High Resolution Rapid Refresh forecast from the National Weather Service.   This system forecasts very strong winds along the coast at 11 AM (blue indicates gusts about 50 mph), with lesser, but still problematic winds (40-50 mph gusts) over the Seattle, with stronger gusts from Everett westward.
 By 4 PM, winds will accelerate further over central and southern Puget Sound.  With many leaves still on the trees and new branches untested by strong winds, expect more power outages.
Be prepared for the increasing gusts and avoid places with a lot of trees.  No biking to the UW on the Burke Gilman trail for me today!  And if you have trees around your home, expect lots of leaves down.


  1. Surprised you didn’t pop a link in there for Seattle WindSatch Cliff. I found it, very cool project!

  2. I got up this morning, expecting it to be windy, rainy and awful, only to be surprised by sunshine and blue sky.

    A huge blue hole opened near Sequim just before 8:00am. It looks ugly to the east, south and north, but blue and wonderful overhead and to the west

    I'm sure it won't last long, but it's amazing what a bit of sunshine does to lift one's spirits in the middle of such weather.

    I'm sure the local Chamber of Commerce will chalk today up to a "sunny day" in order to get to their annual "300 days of sunshine" statistic. Which appears (IMHO) to be calculated according to the "someone saw the sun today in Sequim" rule.

    1. As someone who lives right where the convergence zone ALWAYS converges, I think you should chalk up every beam of sunshine you can get!

  3. Interesting feature on the 1600 map, a streak of strong winds in the Hwy 2-Icicle creek gap?

  4. That 2 AM front was intense in Langley on Whidbey Island. Sounded like a hurricane with the high wind plus extremely strong downpour. Heard thunder just before the wind/rain hit. Most of South Whidbey lost power shortly after (back up...for now). That was one of the most intense rain/wind moments I've experienced in a long time. Unfortunately I don't know what the wind gusts or rain amounts were as my weather station was knocked out without power.

    Hopefully we've lost most of the vulnerable trees/branches before round two.

  5. Gonna need a parade ground sized rake and broom to clean up all the leaves that dropped over night.

  6. Prof. Mass, I just wanted to say I've always enjoyed your blog and I your classes. I've always found you to be the most accurate source of information

  7. Yes, very windy at my place at 2:30 this morning.

    Unless I am mistaken, Cliff, your wind speed vs height graph has the unusual feature of time moving right-to-left. Is that correct?

  8. @ John Marshal:
    "Which appears (IMHO) to be calculated according to the "someone saw the sun today in Sequim" rule"

    You must be new here. If there was sun, it's sunny. That's the definition of a sunny day as far as I've ever known it. Washington isn't for everyone.

    I've got to admit, those sun breaks in the middle of a storm like that are gorgeous. I'll happily take the occasional storm for the sake of getting to enjoy those moments.

  9. > The infrared satellite image at 6 AM shows the swirl of clouds around the low center, located southeast of Vancouver Island.

    Isn't the low southWEST of Vancouver Island?

  10. I didn't pay attention to the forecast and woke up with my patio umbrella in my front lawn! It went over the house!

  11. Pretty intense little storm. Location location location.

  12. @IAMLUCKY13

    "You must be new here. If there was sun, it's sunny. That's the definition of a sunny day as far as I've ever known it. Washington isn't for everyone."

    Actually, I've been here a long time. And it's a joke that you have to live in Sequim to understand. You know, the town with 300+ sunny days a year.

    As per today, with 10h28m of potential sunshine, if we get 5 minutes of sunshine and blue sky, the entire day goes in the books as a sunny day. Even if the other 10h23m were gloomy and rainy.

    It's the only way for the local Chamber of Commerce to achieve its "creative" statistics that they sell to people who want to move here and don't know what Western WA is like.

    But I do agree with you that these brief sun-breaks in the midst of a storm are beautiful. Looking up into the blue hole when everything around is swirling, dark insanity is very nice. Even if that swirly, dark stuff snuffs it out soon afterward, the glow remains in my mind for a while.

  13. Hi Dr Mass,

    The photos looks very similar to a hurricane or typhoon. The wind speeds are not as high as what our friends on the east and southeast coasts get. But what is to stop it from increasing? Can we get typhoons here in Seattle?

  14. Jay,

    We can get hurricane force winds, but technically, as Cliff has told us before, for the storm to be classed as a hurricane (or typhoon, same thing, just a different location) the energy source is a warm ocean with cool air at altitude (delta T in the vertical). That is near to impossible here because of our cold water temps. As far as I know, on the West Coast, no hurricane has made it farther north than about San Diego. Any hurricane that tried to come up here, even on an El nino, would simply run out of gas. The storms we get, mid-latitude cyclones, are fueled differently. Of course, we have only been here studying weather for a couple hundred years at most.

    So the reason we don't get hurricanes (typhoons) is the same reason we can't go swimming!

  15. Sequim is beautiful. Just spent the weekend there- and it was partly sunny. A funny phrase for me, who grew up hearing partly cloudy.

  16. Seattle is being hit hard. Storm season has been crazy. Hopefully these storms do not affect Small Business Valuation. Avoiding trees is a must.

  17. Looks like we may get sky high freezing levels and alpine rain next Tues-Thurs? :(

  18. I live in Moses lake and I have done my own "Sunny days" calculations. I think 250-275 is more accurate than the 300 number they use around here.

  19. My name Caleb and I am 11 years old. My Dad showed me your blog a year ago and I check it everyday. Good job with this blog. Thanks, Caleb


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