November 01, 2009

Sun and Fog

Better than average weather is in store this week.  Virtually no rain in the models until late Thursday, and even that is not a sure thing.  High pressure will be dominant the next four days and in fact on Wednesday there should be strong offshore flow, and temps may climb to 60F and above.

The problem this time of the year with high pressure is fog.  In fact, you know when the foggest month of the year is?  October.  Not December or January.  Why?  Long nights and frequent clear or nearly cloud free skies that allow strong and extended infrared cooling to space.  The fog is most persistent in low areas...such as the Puget Sound basin and the Willamette Valley.

On such nights we often have surface-based inversions in which the temperatures warm with height.  You can watch this happening in real time by going to my department web page that shows the temperatures above Seattle every hour from the profiler at the NWS site at Sand Point:

Monday morning update:  you can see the inversion this morning in N Seattle...times are in GMT (red..14 GMT is 6 AM) 


  1. As models have been showing, the high pressure seems a bit stronger for later in the week with 500mb heights climbing into or around the mid 570`sdm with warm 850mb temps. So it is possible that we may be in for some 60`s for highs later in the week.

  2. The comment on fog in October brought to mind John Keats great phrase (still commonly understood in the UK -- a similar western temperate climate to Western WA):

    Season of mists and mellow fruitfulness!

    Line 25 and 26 also include some interesting cloud observations and associated atmospheric optics that appear at low sun angle typical of the fall:

    While barrèd clouds bloom the soft-dying day,
    And touch the stubble-plains with rosy hue;

    A nice example of a poet making an incisive meteorological observation. If only the AFDs read like that ...

    The full poem To Autumn is here

  3. Anybody know where can I get graphed temperature-altitude data for other locations? I'm used to getting it off the NOAA Aviation Weather site (pilot), but it'd be useful see the graphical rather than textual representation.

  4. Cliff - WTF! 'No rain' until thursday! It's raining outside in seattle right now! :)

  5. raining here in Olympia now. Weird, it was nice and sunny earlier and warm, then poof it clouded up.

  6. I take it back! Fairly significant model failure today. The models all had the showers tonight with nearly nothing south of Everett...much more got through and much earlier. A coastal radar might have helped improve the short-term forecast. But these light showers are the end of it until Thursday night...

  7. We had fairly heavy rain for a couple hours in Bellingham, noon to 3ish. It is really difficult for me to parse out the forecasts as a non-meteorologist with Seattle-centric discussions. I wish we had our own Cliff even if the models sometimes mislead the experts. I might hedge my bets a little more accurately. I'd planned to do some landscaping at that time and instead had to settle for delicious hot Thai lunch and a trip to the local cafe. Sometimes a rainy day is a treat.

  8. wow I thought it was going to be sunny all day after this morning and forecasts I heard. Surprise! Feels more like the holidays - which for early November is appropriate. IT was a nice surprise

  9. we had NO rain in chehalis. it was nice and sunny until 4.


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

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