Monday, July 20, 2020

Why is staying so warm tonight?

I am sitting at my computer right now, with sweat literally covering my face.  It is not cooling off quickly tonight.  And this morning started quite warm, with a very high low temperature.

There is a reason.


We start with warm air over us today, with highs getting into the mid-80s around Puget Sound, 90s in the south Sound and SW Washington and into the low 100s in eastern Washington (click on image to expand).  Warm air associated with an upper ridge.


Each day we have gotten warmer, both for our highs and low (see  temperatures at Sea Tac below)

But something else has been happening that has taken away the crisp, refreshing feel of a few days ago, leaving us sweating tonight...the moisture in the air has increased, as measured by the dew point temperature.  The higher the dew point temperature, the more moisture in the air.  Here is a plot of the dew point at Sea Tac Airport the last few days--major shift upwards from around 50 to 60F.  You can feel that.  

More moisture means evaporation on our skin is less effective.  And water vapor in the air acts as an atmospheric blanket, reducing cooling at night.  Why?  Because water vapor very actively absorbs and emits infrared radiation, and the loss of heat through infrared radiation is how the earth's surface cools at night.

The winds have also declined and wind helps pull heat away from our skin and promotes evaporative cooling.

But compared to the eastern U.S. we have little to complain about. Dew points are in the mid-70s (at 5 PM) over the SE quarter of the U.S.  Very sticky--no wonder folks there are taking their chances in air conditioned spaces.  And no wonder nighttime temperatures stay warm in the SE U.S.


Tomorrow will be a bit cooler and then much cooler on Wednesday as marine air pushes in.

28 comments:

  1. I'm all for cooler, Cliff!

    I used to have a high tolerance for hot temps and extreme humidity when I lived in a hot location. I visited Seattle and couldn't relate to typical temperatures in really hot places. Now, It's happened to me too. I can't take it!

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  2. Why are you serving pro Trump ads on your site. This will be my last comment and visit. Shameful for someone grounded in science to support Trump

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    1. bdseattle....I do not select the ads. Google adsense does based on what it thinks you are interested in and like. It must think you are pro-Trump based on the kind of things you look at. Do you visit Trump websites a lot? But I am disturbed by your comment... so if you don't like the ads on a site, you will reject looking at material on that site?...cliff

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    2. That's right Cliff, god forbid you associate, even digitally, with someone that might have a different opinion that you. SMH. True tolerance seems to be a lost art anymore.

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    3. That's right Cliff. God forbid you associate, even digitally, with someone that might have a different opinion than you. SMH. Tolerance of any form seems to be a lost art anymore.

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    4. Where's the like button for this :)

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    5. Cliff's right about "Adsense."

      I wouldn't ever - ever - accuse Mass of taking ideological or partisan positions. I've followed this site for a long time. If an observation or view appears to fall (or land) in one camp or another, more often than not that seems to be "in the eye of the beholder."

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    6. Temps at SeaTac...Q: Those are airport temps? I've often wondered how much heat the pavement in that built-up urban area affects "the data."

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    7. Liberals hypocrisy.Preach openness and acceptance until it violates one's own beliefs. I am a liberal I believe this will be the downfall of this ideology.

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    8. I see ads for ice cream sandwiches because I was recently looking at ice cream sandwiches online. Really makes you wonder how bdeseattle is spending their screen time...

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  3. So glad you explained this. It has been rough sleeping at night because it just didn't seem to cool off. The air did feel "heavier." Looks like summer has arrived for the PACNORWEST!

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  4. Is this humidity because of the SST offshore?

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  5. Can confirm, I see no Trump adds on this website.

    Thanks for the great work as always, Cliff.

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    1. Neither do I, but someone thinks I need insurance or to refinance my mortgage that I don't even have!😅

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  6. “I am sitting at my computer right now, with sweat literally covering my face. It is not cooling off quickly tonight. And this morning started quite warm, with a very high low temperature.”

    This sounds like the opening lines to a novel…better still I can imagine how the likes of Tennessee Williams or Ernest Hemingway sat in front of their typewriters feeling/remembering the heat and humidity of a summer day. Perhaps that is the way water vapor envelops and inspires the dog days of summer. Art in all its forms...

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  7. The dew point maxed out at 68F yesterday in kirkland...

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  8. Cooled to 59F by morning in NW Bellingham.

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  9. That’s funny, I get adds for women’s tee shirts and ballistic body armor, neither of which I have ever purchased or even searched for on line. So Adsense just fills in the blank if the algorithm comes up with no correlation to the viewers search history

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  10. It's not only the SE region but also the corn belt region in the Midwest where the other day the dew point hit 79 with the day low dew point of 74. A lot of this has to do with the "corn sweat" giving off lots of moisture as it matures. Around here 60 degree dew point is considered comfortable and humid at 65. We actually have higher dew points in the upper midwest than the SE in August, reaching up to 80-85 dew points, occasionally.

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  11. You posted a picture of the upper 48. I will never visit this site again. I hate iowa. 😳

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  12. Gotta' love that marine air always arrives in the nick of time!

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  13. “I am sitting at my computer right now, with sweat literally covering my face. It is not cooling off quickly tonight. And this morning started quite warm, with a very high low temperature.”

    This sounds like the opening lines to a novel…better still I can imagine how the likes of Tennessee Williams or Ernest Hemingway sat in front of their typewriters feeling/remembering the heat and humidity of a summer day. Perhaps that is the way water vapor envelops and inspires the dog days of summer. Art in all its forms.

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  14. Liberals hypocrisy.Preach openness and acceptance until it violates one's own beliefs. I am a liberal I believe this will be the downfall of this ideology.

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  15. Dew point topped out at 80 today in Annapolis with a heat index of 108. Enjoy your cool weather.

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  16. Can you maybe elaborate on the reason for these high dew points? We didn’t (to my knlwledge) Tao in on any moisture, so how is it possible? Also do you predict this will be true early next week when we’re flirting with 90 again?

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  17. I've heard it said that having an AC system installed on my house a few years ago was a waste of money and a luxury. It sure was luxurious to sleep in a nice, cool and less humid house the last few nights!

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  18. Dion is right -- if you can afford the AC system here do it. You're preparing for the future. We have the lowest energy usage in the country so we shouldn't feel guilty about using a little AC when we have to. Now, that being said, don't immediately turn your heat on in the fall just because it got down to 67 in your house...

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  19. It sounds like Google searching ice cream is a reasonable solution to a trump ads (or political ads at all).... hmmm Coffee Almond Crunch sounds good about now given the heat and humidity... Google?

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