May 23, 2017

Major Marine Push Occurring Right Now


This is really turning into a very unusual (and strong) onshore push event.  Over 10,000 customers have lost power in Western Washington (see PSE map)

The wind gusts were amazing...several locations in the central and eastern Strait of Juan de Fuca got to 50-60 mph--even southward into Puget Sound.  Exposed area in the Cascades gusted to 60-80 mph.

Smith Island, just off northern Whidbey, reached 67 mph (58 knots)! (see below)

Aircraft landing at Sea Tac Airport have reported low-level wind shear on final approach, as indicated by the pilot report (PIREP)

KSEA UUA /OV SEA/TM 0315/FL005/TP B737/RM LLWS +15KT 005-SFC
Winds are northerly at the surface but southerly a few hundred feet aloft._

The Guemes ferry is stopped due to swell. Anacortes is out of power.  Pretty wild stuff.

A huge pressure difference has developed between the Washington coast and the western interior, resulting in a rapid increase in onshore winds.  In some locations, such as the Strait of Juan de Fuca, the winds are blowing as high as 50-60 mph right now!

This table shows differences in pressure (HR is in UTC, 23 is 4 PM).  The Hoquiam minus Seattle pressure difference was up to 5.2 hPa (higher a Hoquiam).    That is HUGE (to quote our President) and always provides a good blow. That will push winds in from the west.

Here are some of the maximum gusts as of 5 PM.  59 mph at Race Rocks at the SE tip of Vancouver Island.  Lots of winds between 30 and 50 mph in the Strait.  40 mph in Shelton.  And it is getting gusty even here in Seattle right now.

The winds at buoy 46088 and Smith Island in the eastern portion of the Strait show accelerating winds to roughly 45 knots (52 mph)...and they aren't done revving up yet!  Fun day to take the Clipper to Victoria.

This situation is a good example of a Northwesterly Onshore Push, a rapid inland surge of marine air initiated by the passage of an upper level trough (see an upper level forecast map for 5 PM below to see the trough).

We had warm air and low pressure over region before the trough, and behind the trough there is cooler air and higher pressure.  The result is a large pressure change (or gradient) and the replacement of the warm air by cool, marine flow.  Known as an onshore or marine push in the weather business and very typical this time of the year.

Tomorrow will be much cooler day, with temperatures falling back into the mid-60s.  But don't get rid of your sunscreen and shorts yet...the ridge of high pressure will rebuild later this week and temperatures will quickly surge into the 70s and low 80s by this weekend.


  1. Thanks Cliff!
    Blowing quite hard for late May...
    Lots of damage to fragile young crops.

  2. I was in Maltby when this really picked up... branches were coming down everywhere. Saw a tree down in Monroe too. The winds were pretty impressive for this time of year!

  3. "Major marine push" is right! Lost power for about an hour here on Bainbridge Island. Don't think I can remember a marine push causing an outage before.

  4. I went into Costco; it was sunny and warm.

    Came out of costco; the marine stratus had taken hold.

    Guess I should close the windows in the house and start conserving heat for the night.

  5. Blowing hard all day on the Sequim Prairie. The pollen count must be off the charts.

  6. Just spent 2 hours with State Park staff cutting away fallen alder from our trailer in Bay View state park! No time to do full inspection but right now looks like broken vent cap and some rubbing. Daylight will tell.

  7. Here in Downtown Greenbank ( Whidbey Island ) itz been blowin' like hell since VEREEE early Tuesday morn = ALL day Tuesday... Tuesday nite & now into Wednesday (early) morn.

    I went into Seattle to Jazz Alley last nite = NO winds enroute - in Seattle - nor homeward bound ... TIL' I got off the Mukilteo-Clinton ferry & hit Freeland.

    Cliff... this ''marine push'' = a pain-in-the-tush ! :)

  8. It was quite a shock. I rode my bike to work. Went out at noon and it was high 70's. Rode home about 6:00 and it was 57 degrees. Against the wind I about froze.

  9. It seems the wind always blows from the south in storms but was reversed yesterday. That was weird and I think why so many branches broke. The temp dropped 20 degrees in an hour before sunset. Surreal weather. I drove home from work under the felled tree featured on KOMO and recall worrying about them as I passed. Speeding up wouldn't necessarily help, I thought.


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