October 02, 2022

Valley Smoke and Endless Summer

 We are now experiencing the most sustained extension of summer weather into autumn in many years, with one of the symptoms being the longevity of some smoldering fires over the region.

And the smoke from these fires reveals some interesting aspects of local meteorology and the effects of terrain.

Yesterday afternoon one could see smoke plumes from the Bolt Creek and Lake Wenatchee fires heading westward toward western Washington.  Solar heating during the day reinvigorated the fires and helped mix the smoke vertically where it was caught by the easterly (from the east) winds of the lower atmosphere.

NASA MODIS Imagery around 1 PM, Saturday

Overnight, as the surface and lower atmosphere cooled, vertical mixing was greatly weakened and the cool air tended to move down-valley towards lower elevation...on BOTH sides of the Cascades.  

To illustrate, take a look at the visible satellite image around 8 AM this (Sunday) morning.  

Smoke from the Bolt Creek fire was moving westward down the Skykomish Valley into western Washington, while the Lake Wenatchee fire smoke followed the Wenatchee River Valley eastward into Leavenworth and the Wenatchee area.


Both of these "valley smoke flows" spread out as they gpt out of the mountains.

The smoke not only undermines air quality, but also affects clouds.    Look carefully at the Snohomish River valley east of Seattle--can you see the fog there?

This fog is enhanced by the smoke from the Bolt Fire, whose smoke provides small particles upon which fog droplets can form.

The PurpleAir air quality observations clearly show the unfortunate implications of the smoke (see below).  The Bolt Creek smoke plume is exiting around Monroe and then swept southward over the eastern suburbs of Seattle.  MUCH better air quality near the Sound.


The Wenatchee River smoke plume is associated with very bad air quality from Lake Wenatchee through Leavenworth to the Columbia River.

Tomorrow (Monday) will be similar...sorry.

The Problem

The atmosphere is stuck.  The atmospheric circulation has been locked into a very stable pattern with a ridge of high pressure over the West Coast and two troughs on both sides--called an Omega Pattern.

Take a look at a series of upper-level maps (500 hPa, about 18,000 ft) showing heights above sea level (you can also think of this as the pressure at 18,000 ft).  Red colors indicate ridging/high pressure and blue/greens are the opposite.

This morning there is a ridge over the western US and troughs on both sides.  An omega pattern).


The situation late Thursday is similar with even higher amplitude.  This means dry and warm over the Northwest.


And the forecast for October 12th is simply extraordinary. An omega pattern on steroids.


We may not see a single drop of rain before mid-month.  Have we ever had a completely dry first half of October?   

Here is the data for Seattle....the answer is yes... several times.


Strangely enough, this hot, dry pattern will prevent new wildfires over from western Washington and Oregon, as well as California.

Why?  Because it is not the pattern that will produce strong easterly winds over the Cascades--that requires a pulse of cool air and associated high pressure immediately to our east.

Atmospheric Sciences 101

Like last year, I am teaching atmospheric sciences 101:  a general introduction to weather and climate, this fall.  You can learn more about the class on the class website.  I talk about everything from the basics of the atmosphere to weather prediction, thunderstorms, hurricanes, and local weather to global warming and climate.

I will be teaching the class in person at the UW, but will also make it available over zoom.  Thus, folks can take it remotely.

If you are over 60, you can take the class through the ACCESS program for a very nominal charge (something like $15).   Last year I had over 125 folks do so.

So if you are a UW student looking to learn about weather or a non-student interested in the topic, I welcome you to join me this fall.  My first class is on September 29th.


29 comments:

  1. so sick of this weather, an endless series of suck. Well past time for a huge wet pattern to signify the long - awaited pattern change into Fall.

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    1. Really? I'm still recovering from the 9months of rain from last winter. Always be careful what you wish for. Experience tells me to appreciate every one of these "bonus" days as winter will soon be here.

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    2. I don't consider this weather a bonus in any way. It's smokey and everything is so dry that the city is dusty, dry and ugly looking. It's not pleasant (or healthy bc of the smoke) to even be outside right now.

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    3. Bonus to what? More days of Smoke Season?

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    4. I'm with Eric -- I moved here from Boulder because i wanted 9+ months of rain and fog!

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    5. Anyone that legitimately wants nine months of rain and fog needs serious mental health intervention.

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    6. I'm with Eric too. There is nothing enjoyable about smoke and unseasonable warmth.

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    7. I'm with the catguy! Also if you want that kind of weather feel free to move to Juneau and report back. I'm always fascinated by the weather there. Rain and fog daily.

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    8. I'm with Jimmy and Thecatguy. Summer started waaay too late this year. Felt like the 90s again. "It stops raining on July 5th". We can get our first rain in December as far as I'm concerned.

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  2. I'm just wondering how many of these rainless first half of October's were preceded by 3 and a half months of no rain, little sprinkle's don't count.

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    1. As far as I can remember, it used to be that we got a good soaking late August, and a wet pattern during the late part of September, followed by a dry first part of October, then back to a wet pattern. This year is surely unusual.

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    2. William, Yes, that's how I remember it when I first moved here in the 70's. A spell of rain in late August and at least one in September.

      While I love the sun, bad things start to happen when one goes too long (4-8 weeks) without rain. Of course the ideal would be 4-6 sunny days, then a T-storm at night with an inch of rain, repeat, repeat... Not an order that Mother Nature can fill in the PNW, however. It is feast or famine here.

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    3. That sounds wonderful ... here's hoping that's what we'll get next year. If I wanted to live somewhere dry, hot, and smoky, I would've stayed in CA.

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  3. We use your posts to plan sea kayaking trips in Puget Sound and Canada, and hikes in the mountains. We also Windy.com, which allows us to select the elevation that we want to see the winds at. Common sense says to use surface winds for kayaking, and for hikes, the elevation that we will be hiking. Is this the correct approach?

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  4. The more interesting question to me is whether we have ever had a "completely" dry August through October 15th period.

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  5. For those that question this phenomenon, it happened in 2012. I know, I was in the midst of loosing my mother that October, and it was one of those summers where the summer dryness didn't show up until mid to late July, and it stayed very warm and dry through much of that October and on the day she died, it rained much of the day for the first time that fall. October 27th, 2012. This was in Tacoma, but the effect was similar elsewhere in the region.

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    1. I remember that. 87 days without rain in Seattle. I'm so sorry about your mom.

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  6. What webpage does the last graphic of the October precipitation come from?

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  7. I have a couple of breathing issues, due to heart problems...this relatively minor smoke thing bothers me a lot...I guess I will feel better in a couple of weeks?.....maybe!

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    1. I'm also physically sensitive to even "minor" levels of smoke. Thanks to covid for supplying me with a ton of kn-95s for when I have to go outside, but I'm so angry to miss the nicest part of the year for opening windows and taking long walks

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  8. A double Indian Summer.. nice! One correction.. it's the Snoqualmie river valley east of Seattle.

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  9. The last time we had notable rain in the Olympia area was June 16th if this dry spell Extends to mid October that will be 120 days with basically no rain where I live! that's extreme in my book, see past months and years of recorded precipitation, NOAA has a pretty cool site where you can cheek past weather, click on the map for your state the chose your city, year, month, I use Daily data for a month, https://www.weather.gov/wrh/climate

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  10. If you've lived here for a while, you know the 3rd week of October is when the rain hits. This is very normal. The smoke is the new normal.

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  11. Cliff, is an Omega block the same thing as a Rex block? I learned that term recently somewhere but still am not sure what it means.

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  12. Inconveniently enough, the one day of meaningful rainfall I saw in all of September was the weekend I went backpacking in Rainier National Park. 35 degree low overnight at about 6000 feet, and while I didn't have a rain gauge, I'm guessing at least 1/4" of rain, since it was steady for hours and had a period where it was relatively heavy.

    That inconvenient timing aside, the lack of rain is difficult for me, but at least there is fog most mornings to help.

    Interestingly, many trees absorb water from the air through their leaves / needles. Douglas Fir do particularly well at this in our region, so hopefully not too many trees will die from this extended dryness.

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  13. Go away summer - you've vastly overstayed your welcome.

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  14. Loving every day of this extension of Summer. Helps make up for the inordinately long and cold winter/spring, which was kind of hard to endure this yr.

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