September 20, 2009

Super-Ridge and Late September Heat Wave

Last week I was in California...dropping my son off at college and visiting Yosemite Park. It was hot down there...even reaching 90F in the Yosemite Valley, but that is nothing compared to what is going to happen during the next few days--both down there and up here in the NW.

Take a look at the temperatures of the past two weeks (see figure above). In general, the high temps have been at or above normal...and the minimum temperature much above normal. But real heat is about to turn on.

A huge, high-amplitude upper ridge is developing over the west coast (see forecast for Tuesday morning). This is really amazing...with unusually high pressure developing aloft and at low levels. Such a major ridge is associated with warm temps aloft and with offshore flow and added warming at low levels. Look at the computer forecast for Tuesday (see figure). Very, very warm temps in California, offshore and downslope flow over the Cascades, warming over our region. Notice the development of the "thermal" trough into western Oregon and Washington....the classic warm weather pattern.
Western Washington should surge into the mid-70s tomorrow and mid-80s on Wednesday and Thursday. Impressive for late September! And I have no plans to return to California where temperatures of purgatory will abound. A heat warning is up for the SF Bay Area where some interior locations will get well into the 100s. Yosemite Valley will be in the mid 90s.
And don't forget the Willamette Valley...where temperatures will climb into the 90s. The Willamette is often 5-10F warmer than the western Washington interior...frequently even warmer.


  1. Noticed Brookings already hit 89 today with surrounding areas considerably cooler. Reasoning for that in Cliff's book. It'll be interesting too see how this could be a heat wave in localized areas, such as a downslope region like Brookings. And makes you think what temperatures would be like again if it were early july and not late semptember with such conditions.

    PS. Short story about that, last weekend planned an outside basketball game on Sunday in Ellensburg. Forcast called slighty cooler than the day before of 90 and wind. Every reason for, 850mb and 925mb temps. down a couple from the day before. But they didn't factor in that wind you can almost set your watch too here. Anyway the temperature spiked to the upper 90's the hour right before that cooler west wind. With the way that September sun hits ya made it "feel" like the hottest day of the year outside. Miserable game! Nerdy story!

  2. Maybe we'll see those noctilucent clouds again? Of course, this time it may not be due to the heat...

  3. Yes. Nice fall pattern (offshore flow over the coastal ranges and red flag warnings).


    Every few days I type El Nino into google and check recent news articles to see if El Nino looks to be stronger or weaker this year. I am hoping for a snowy winter again this year and according to this article maybe el nino wont be as strong as originally thought.

  5. The strong easterly winds were blowing well this morning in the Snoqualmie Valley. I left at 8:30am and my personal weather station had a temperature of 76 degrees. I noticed a couple of smaller deciduous trees that had been uprooted, they don't stand much of a chance when the winds blow and they haven't lost their leaves. My car was also showing 76 and the temperature dropped to 56 by the time I reached West Lake Sammamish parkway.


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

A Drier Than Normal Spring over the Pacific Northwest

I had to water some new plants today because the last few weeks have been relatively dry.   So I was dry has it been in our ...