December 30, 2008

Windstorm Doesn't Look Likely

I just took a look at the latest model runs...and I am not expecting a major windstorm anymore. As noted earlier, there has been a lot of disagreements between models, even today when we are within 48hr of the event. Something is making it difficult for the solution to gel...and I think I can tell you what it is.

Take a look at the upper level forecast chart (500 mb--about 18K ft, solid lines give the height of that pressure surface above sea level) for 1o AM on Thursday. There are two upper level troughs (I have marked them) that are interacting to form the incipient disturbance. The phasing of these features is critical and this makes the development of a storm much more difficult...small errors in the speed of either trough will change the forecast. Furthermore, if they don't join, then you can end up with a complex, multiple storm that can't amplify effectively.

Take a look at the 48h forecast of sea level pressure...there are in fact two low centers. This is bad. I have been looking at windstorms for years...and my experience is this kind of multiple structure is the kiss of death. And the models know it.
So you can forget a Chanukah-Eve or Inauguration Day type storm event.
Tonight, a low center is moving way north of us over the Queen Charlottes...and rain associated with a trailing frontal band has reached our area (see imagery). If you look closely you can see the circulation over the southern part of the Queen Charlottes. The front assoicated with the low will be through by daybreak and then we will get into the cold,unstable air. Showers in the lowlands, breezy (winds 15-30 mph), cool, and lots of snow in the mountains. One final note...after the "storm" get through on Friday AM we could have some lowland snow showers, particularly in a convergence zone. But we can wait on that....

PS: Several of you have asked about good amateur equipment for observing the weather. I and others in the dept think highly of the Davis Vantage Pro equipment...really good value for the money...and high quality instruments. But anyone can start cheaply...a digital thermometer and rain gauge can be purchased for 30 dollars total. Add a cloud chart and it is nice starter for a budding young meteorologists.


  1. Great blog post Cliff. I saw the operational runs of the GFS suite come out here and saw that "two-phased" feature and knew immediately there would be no major windstorm. In reading the NWS Seattle Discussion at 2030 tonight I noticed a mention of lowland snow if that track is far enough south. That would be interesting and you did talk about this in an earlier blog. Good work & we'll see what tomorrow brings! Peace.

  2. With arrows, even! You've exceeded your own expectations :-)

    In all seriousness, the visualizations that you have to work with are quite amazing: rich use of colors, overlaid images, symbols. I find myself wondering how I could apply that level of imagery in my own (completely unrelated) field.

  3. Thank you so much for your willingness to communicate (frequently and cheerfully) with us out here.

  4. I have a LaCrosse 2316U that I purchased from Costco for about $80. It does the job: wind, rain, temp, etc.. I even figured out how to post it up. Pretty easy schmeezy.

    Sedro-Woolley Personal Weather Station Data

    Our Fire Dept installed a Davis Vantage Pro about 3 years ago, and just 4 weeks ago I convinced the IT guy in the city to post it to the 'net too.

    City of Sedro-Woolley Weather

    Both are for Sedro-Woolley and the difference in location is about 1/2 mile and 150feet in elevation (1st one is on a hill).

    Thanks again for all your insight, Cliff. I like my news right off the bone. No fluff or drama.

    Bow Down!

  5. I've been addicted to this report and read it more than my own email. I have begun to look at everything in terms of weather systems; This morning in the shower the hot water made the heated air rise out of the shower causing a low pressure situation which caused the cooler, high-pressure air mass from the rest of the bathroom to push the shower curtain inward and it stuck to my butt. I will not be including a radar image.

  6. Olalla: 37, moderate rain, little or no wind - 10:55 pm

    My tolerance for stormy weather would be greater if it wasn't so frequently accompanied by power outages. I think the highway interchange job just down the hill from us may be helping this winter, because the tree people came all the way up the road this summer and did the most thorough job of pruning branches and trees near the power lines that I've seen in 15 years at this location.

    - Pete

  7. Thank you, Cliff, for the daily reminder that science rules. And thank you "signalius" for the science fair moment which provided me the biggest smile of the day. :)

  8. Question for you Cliff... one thing I never understood - why do they call them 'disturbances'? Where did that term come from? Thanks!

  9. Check out the latest NAM...(NAM is one of the forecast models Cliff always talks about). Anyone up for more snow???

  10. Why the differential forward motion of the two lows, why was the northern faster in the end. The northern one was at the northern edge of the strong pressure gradient, the southern one in the midst of the pressure gradient field.

  11. Just discovered this blog. One of the best I've read. So, why do all the "chief meteorologists" on the local news continue to forecast a "major"storm? What information are they not using? Or choosing to ignore?

  12. Pretty windy in Port Townsend last night - lost power for a bit.

  13. Thanks for your insights, Cliff.

    If the models don't verify, are they tweaked in any way to improve their reliability, or are they self-correcting?

    Thanks and happy new year.

  14. Signalius--my son (age 7) and I would also like to thank you for the "science funny" and for the resulting big laughs.

  15. "This is bad. I have been looking at windstorms for years...and my experience is this kind of multiple structure is the kiss of death.... So you can forget a Chanukah-Eve or Inauguration Day type storm event."

    These phrases made me smile - at first I thought that "bad" and "kiss of death" referred to having a windstorm, not missing out on one! Just confirms to me that I'm in the right place on this blog; I love "big weather" and it's obvious that you do too, Cliff.

    Thanks so much for this great blog, which my students will all be required to visit regularly next fall!

  16. Lake Stevens this morning around 8am, freezing rain (or sleet?) with lots of ice covering everything.

    5 miles south of lake stevens on a higher hill it was snowing moderately (along hwy 9 at least).

    I take this as a sign we'll see more snow in the next 2 or 3 days after these passing 'wind' storms go south.

    I'd prefer the windstorm this weekend, but snow will do fine as well. :)

  17. Signalius, I laughed until I cried!

  18. Some model images are suggesting a brief but intense rain-on-snow event on New Year's Day - i.e., from 2-5 inches of precip at up to 36-40 degrees F at the southern end of the Puget Sound drainage. For those who care more about floods than wind storms, any comment on whether this is a reasonable scenario? Entertaining blog, otherwise...

  19. CLiff, what's your latest read on Thursday/Friday/Saturday? Will we get stong winds or snow out in Duvall? Both?

    Thanks for keeping us informed.

  20. BTW, snowing hard in Duvall at 11:30am Dec 31st, 34F.

  21. East Bellevue at 210', wintry mix.

    This just in from the Seattle Times... we WILL be using salt on heavy snows going forward...
    Seattle to Use Salt in Future Storms

  22. Snorain falling 580 ft elevation, Demery Hill, Sammamish.

  23. So very glad to have the probability of a windstorm discounted; I've got a Miltonia orchid with buds developing, and would prefer to keep the heat on.

    I stopped keeping a rain gauge when the third one died of a hard freeze, but had one long enough to confirm quantitatively something I'd long known on a qualitative basis: the Olympia Airport NWS station is much drier than my house. There's a set of climatological maps in Franklin and Dryness' The Natural Vegetation of Oregon and Washington which are instructive about how much variation in rainfall there is west-to-east in the small span of Thurston County.

    I know why the official weather observation stations were set up where they are (hey, I've been listening to you since you first started on KUOW, back in the mists of time) but I'm wondering how useful amateur observations are for weather and climatology pros?

    Speaking of which, heavy rain over night in Union Mills, currently 38.7, low in the past 24 hours 30.7, high 38.8. And I still have LOTS of unmelted snow on NE facing slopes. I'm girding my loins to go face the mud and chill and record that.

  24. Regarding your blog entry, “Windstorm Doesn't Look Likely”, for the 30th, Tuesday, ....

    As best I can put it Cliff - (i.e. from a simple “Wx Enthusiast’s” point of view), .. Instead of looking - more finitely, at different specific variance in pressure gradients, .. couldn’t the general weakening of the pressure slope that you’ve pointed to, this together with more specifically, the main strength and intensity of the general system energy forecasted previously, .. be looked at and explained more simply as being associated with (i.e. the result of) the general retraction/recession north of main-source cold air mass .. progressively since the 26th or so, .. this together with also at the same time - (where still distributed through the main midlatitudes, broader Northern Pacific), main cold air’s concurrent slower movement more longitudinally eastward over the past few days ?

    Wouldn’t this main movement and distribution of main-source cold air be more responsible for pressure gradient variance, than the other way around ?


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