One of the most extreme days in western Washington history....and why the lowlands are protected from surface smoke

 Yesterday (Sunday), was one of the most extreme high-temperature days in western Washington history.  

 In some ways, almost the equal of the June 2021 heatwave.

Consider a map of the high temperatures on Sunday (below, click on image to expand).  88F at Sea Tac and lower 90s in some locations.  

Amazing for mid-October.


 As noted in my previous blogs, this heat was associated with strong easterly (from the east) winds that warmed by compression as they descended into western Washington.

Now let me convince you how unusual this was.   Consider Paine Field in Everett.  At this station, the temperature reached 87F--the warmest October day on record at that location.  The runner-up was 4F cooler.  SeaTac had its second warmest day on record, with the warmest day being on October 1.

October Records


But let me impress you even more.   

During the June 2021 heatwave...the greatest in Northwest history... SeaTac Airport jumped to 108F, 17F above the previous record high for the date.  On Sunday, SeaTac hit 88F, 16F above the previous record for the date. 

At Everett, the high of 87F on Sunday was 29F above the typical high for that date, while on June 28th, the 100F temperature was 31F above the normal high.

The bottom line:  yesterday was extreme and rare.

Smoke Protection

Today, a lot of smoke was blowing overhead but air quality was decent at low levels.

Why?

To show the smoke, here is a visible satellite image around noon.   It looked like something out of Dante's Inferno!  Later satellite imagery looked similar.


But the air quality map around 6 7 PM showed decent air quality around Puget Sound, with the worst conditions around Olympia (expected due to numerous smoke-filled rooms).


It turns out the something was protecting us living at lower elevations, preventing the smoke from mixing to the surface.

The name of our friend?    The Inversion.

Inversions occur then the temperature warms with elevation.    Inversions suppress mixing.

Why did we have an inversion?  Because cool marine air at low levels moved in overnight, while warm air remained aloft.

That produces an inversion.

Here is a plot of temperature (red line) and dew point (blue dashed) from the launch of the balloon-lofted weather station (radiosonde) at Forks on the WA coast around 5 PM this afternoon.   Around 5000 ft the temperature increases with height.  That is the inversion!

temperature days in western Washington history One of the most extreme days in western Washington history....and why the lowlands are protected from surface smoke

The inversion should weaken but remain in place on Tuesday so I expect our air to remain breathable.  But air quality will slowly degrade over time until Friday, followed by rapid improvement as rain and wind move in.

For Seattle, the biggest problem is the Loch Katrine fire, which is low and close, providing less "inversion protection."


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