July 29, 2009

One Record Down, One to Go?

Looking at the hourly data at Sea-Tac Airport, it appears that we have broken the record for highest minimum temperature in Seattle history. It was 69F and so far today the airport has only dropped to 71F, and it has subsequently rise...so that is probably it. This is a major record to break. At 9 AM Sea-Tac is 88F, 10F ahead of yesterday (due to the downslope flow). We are probably going to break the all-time record high--will be hard to stop it now.

Now, what about the high temperature record--of 100F. Yesterday probcast was giving the most probable maximum for the airport of 101F (by the way, so many of you have hit the site that it appears to be unavailable now--there is a major power failure on campus, probably heat related, and the building with the computer server is affected). If we do this, it will be close.

The sand point profiler and surface observations indicates that temps are warmer the lowest thousand feet or so, but slightly cooler air has moved in aloft (see figure, time in UTC, 2912 is 5 AM, heights on left in meters, red lines are temps in C). This air is associated with southeasterly flow that has developed aloft. This was forecast yesterday--high pressure building in east of the mountains has reversed the east-west pressure gradient, producing offshore and downslope flow. Downslope flow produces compressional warming and works against the cooling northerlies that often develop in the afternoon over the central Sound. But cooler air aloft obviously works against it. The models and probcast suggest the balance will be towards warming today. Below is the latest night's high resolution (4-km, WRF model) run for this afternoon at 5 PM, showing temperatures at 2 meters (surface temps). Note the zone of above 100F than includes Sea-Tac.
The Willamette Valley is much hotter--several locations will get to 105F. Their lack of proximity to water makes that area an oven in these situations and they are often 5-15F warmer than the Puget Sound region.

Anyway, more later...this is going to be close.


  1. What are/were the old records?

  2. 106°F at PDX yesterday was miserable.

  3. A friend of mine called me from Days Creek Oregon (south of Roseburg) last night at 10PM, and reported the current temp there then at 91F. Earlier in the day it had made it up to 108F. That's hot!

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  5. Prof. Maass, one of the defining points of this heat wave has been the dewpoint, which has been pushed well into the 60s. In most of the local heat waves I can remember, the dewpoints have remained in the 50s, the air masses retaining the feel of the desert from which they came.

    With our copious amount of open water in Seattle, you can only blow so much dry heat into the city until the lakes/vegetation start evaporating heavily.

    Would you agree that this heat wave is running unchecked in part due to the decreased evaporative cooling capacity here at the surface?

  6. Cliff: Your comment about the intensity of the Willamette Valley heat makes it sound to me as if the ONLY reason it's so much warmer there is due to the lack of a water source such as Puget Sound. Isn't it also because it's a simple fact that, in general in these situations, it's warmer as you travel further south (heights are higher, I guess . . . )? Obviously, Medford is consistently warmer in the summer than the Willamette Valley, Redding CA is still warmer, etc.

  7. Officially 83 in Everett at 7:53 a.m. Has such a thing ever been seen before? . . .

  8. Lindsey: the Willamette Valley is also colder than the Puget Sound in winter.

    You can see the same effect between Seattle and Olympia (for example).

    That lack of moderation is a significant effect ... if the sound didn't exist "Seattle" in the "Puget Valley" would be rather similar.

    The solar radiation at the surface does increase a bit as you go further south but not as much as to give these changes in temperature. You can see this in the maps of average july temperature. There is a few of degrees difference between the Sound in the north but there is only a couple of degrees difference from PDX down to Medford (though Medford is a little warmer).

    There is also the effect of the thermal trough moving northwards from California too so the valley tends to get the heat first and for longer.

    It's all in Cliff's book :-)

  9. Even Portland was only 79 yesterday at 9am. Portland is 81 right now. So 88 in Seattle at 9am??

  10. Kevin, thanks. I have the book but must admit I haven't really looked at it yet.

    I don't want to bore people with minutia, but I'm not completely sure of what you're saying. Olympia (and many parts of the Willamette Valley, for that matter) gets consistently cooler on a clear night than Seattle any time of year. But the days are slightly warmer, at least in the Willamette Valley, and that includes winter. (I really only consider daytime maximums in comparing temps in these kinds of discussions.)

    I guess your statement, "The solar radiation at the surface does increase a bit as you go further south but not as much as to give these changes in temperature" is key. All I'm saying is that the difference in temp is "more" than JUST the "water" issue, which was the point of my original post. I'm actually very appreciative of learning what you and Cliff are saying, that it's more than just being further north that creates the temp difference.

  11. The east winds just kicked up in Troutdale causing the temperature there to jump 8°F in the past hour. They're now 87°F, +7°F over this time yesterday.

  12. KOMO is saying it is 90 degrees at 9:05 AM

  13. The lack of proximity to the water is much more significant than the latitudinal difference between the Willamette Valley and Puget Sound....cliff

  14. 93 degrees at 10am... is this amazing rate of increase going to slow down anytime soon?? At this rate we're going to set a new all-time record by Noon.

  15. Thanks, Cliff!

    Seatac 93 at 9:53 a.m. I realize it can't keep climbing at this same rate until 4 p.m. or whatever, but surely we'll break 100 with ease, right? . . . Could an official revision to the forecast be coming? . . .

  16. Uh, Seatac is ten degrees warmer than Renton, Tacoma & Olympia, and eight degrees warmer than Boeing Field at 9:53! I have to think things will generally even out at some point today (even given that Seatac is known as kind of a "warm spot"), and I'm guessing it will be closer to the rate of those places with lower readings. But still . . .

    (OK, my own rate of postings will now decrease :-).)

  17. At 10:20am it's 92.7C at Volunteer Park, Seattle.

    Not a "legal" station -- it's a roof top station on Seattle Asian Art Museum (you can see it from the "Black Sun") but it's the closest and most accurate to my (tarmac surrounded) south facing apartment.


    Urban temps are going up ... dew point is dropping but still just above 60F.

    My third floor apartment internal temp (with a multiple extractor fans and aluminum foil on the windows!) is 90.5F. It peaked at 93.7F yesterday evening. At 6am it was 87F probably the overnight low ... :-(

    Waiting for the marine push.

  18. I am originally from the Keizer area of the Willamette Valley, just north of Salem, and I still have family there. One saving grace has always been an evening sea breeze which cools everything down so people can sleep, but the last few days there has been no breeze at night. I have noticed, since moving to Olympia, how much arid it feels in the evenings down there as well.
    NOAA predicts 109 for Keizer today. Very few people have AC there...

  19. That should be "much more arid"..

  20. 10:45 am and 98.3 at the Phantom Lake Elementary School Net weather station. The weather station 0.8 miles from the school on my roof says 98.5F.

    If you're going to do something, GO BIG.

  21. I guess a watched pot never boils ... the next SeaTac update

    KSEA 29 Jul 10:53 A Few Clouds 90 63 41 W 6

    That's down 3 degrees from the previous reading.

  22. Yep, Kevin, you get those winds shifting to westerly off the Sound and temps drop. I wonder how high it got between hours. And I wonder if the NE / E winds will resume.

  23. Well, Everett (!), and Renton have risen to 93, and Boeing Field has popped up to 91, which still shows a general trend of rising temps. Should be an interesting afternoon.

  24. Lindsey:
    I believe what they are saying is that Puget Sound acts as a huge buffer, moderating/regulating the temps of the area surrounding it.

    With that much water, at a relatively uniform temperature, if the air is much warmer than the water, the air will be cooled; and vice versa for cooler air.


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