October 28, 2009

Warm, wet and breezy

I am finally ready to talk about the upcoming wet weather--I had to wait until the solutions settled down. This week there were major shifts and changes in the forecasts, not only of the winds but for precipitation as well. The reason for the lack of predictability have been ETs--extratropical transitions. This is when tropical systems move northward into the midlatitude westerlies. As the tropical systems move poleward they transition into midlatitude or extratropical systems and this transition is very sensitive and can induce weather disturbances far afield. Sort of like a freeway entrance....hard to judge exactly what car you will be behind as you accelerate into the traffic.

Well, if you haven't been able to go to Hawaii, Hawaii is coming to you!

A warm front is now approaching our area, bringing clouds and light precipitation (see image above). Most of the rain will be done with by 10 AM and there should be breaks tomorrow afternoon. The 24-h precipitation ending 5 PM shows modest rain over the lowlands, with heavier amounts (1.5-2 inches) southwest of the Olympics and Mt Rainer. Nothing major. But you will notice the change in air temperature tomorrow as much warmer (like 20F warmer) air moves in aloft (see temps at 850 mb--roughly 5ooo ft). Bad news for snow levels. Major melting of today's snow will occur.

But then the second act will occur...the arrival of the premo moist, warm air from north of Hawaii and the cold front. A long thin conduit of moisture from Hawaii to the NW will be apparent on Friday afternoon--and at that time it will be headed for BC (Figure). The infamous PINEAPPLE EXPRESS.

Later on Friday and early Saturday the plume of moisture will sag down over Washington ahead of the cold front. So later on Friday night it will be our turn. Amounts will be substantial over the N. Cascades, perhaps producing minor flooding for rivers there, but not a really serious situation because the front will move through quickly (see graphic showing 24-h rain ending 5 AM Saturday). The worst flooding situations occur when the plume stalls over us. Amazing rainshadow over Sequim and vicinity. By Saturday afternoon it will be through, with postfrontal showers. No major threat for the Green River valley.


  1. Cliff,

    With the cold front, do you expect there to be gusty winds or just breezy?

  2. i'm confused here..........
    if this is an el nino year, why does my rain gauge read so far over 4 inches of precipitation for the month of october in ballard? more is on the way.
    last year it recorded 1.88 inches for the entire month--not an el nino year.
    doesn't el nino mean warm AND drier for the northwest???

  3. This wont be a major windstorm, but it will get quite windy on Friday. Strong winds, possibly damaging, over NW Washington.

    It is an el nino year, but the el nino influence does not snap in until after the new year in general

  4. Thank you for keeping us informed in regards to the green river valley. It's been very helpful.

  5. Cliff,

    At this point, what do you think the conditions will be for the Sounders playoff game at Qwest tonight (7-9PM)?

  6. Hello Cliff,

    What do you think the conditions will be for the Sounders playoff game tonight at Qwest (7-9PM)? You're blog indicates current rain moving past us by that time, others are saying continued rain?

  7. We picked this weekend to go to Kalaloch for some beachcombing and maybe a photo trip up the Hoh Valley. If the storm is heading north toward Vancouver Is. does that mean we'll be spared the brunt of the rain? :-p

  8. Noticed Central B.C. taking the brunt of this storm. Several 12 hour periods of 2-5 inches. Know of any rain gauges up there? Intresting too that all the 72hr models still show a large residual pool of moisture far to the SW so we'll have to see how that interacts with the weather pattern next week.

  9. "Strong winds, possibly damaging, over NW Washington."

    Those are some strong words if you live in Bellingham or points North and West. Seattle Office has no watches out. Should they?

  10. its been really gusty here in chehalis today.

  11. Josh, according to Scott Sistek at Komo we should be expecting some warnings to pop up here soon.

    I've read winds up to 45 and 50 for the northwest part of the state. Seems good enough for at least some concern.

    Still, I'm in Lake Stevens so not expecting too much, would be nice if we got some good winds though!


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