Air Quality Worsens Over Puget Sound this Morning

 I walked outside this morning in north Seattle around 6:45 AM and the smoke smell was very strong.   The expected worst (and last) day of the smoke is here and it is nasty.

The Seattle PanoCam this morning at sunrise clearly showed the shallow smoky miasma over the city.  Even the tops of some of the tall buildings are above the worst of it.  


 The calibrated Purple Air air quality sensors this morning shows the plume of terrible surface air quality exiting from the Skykomish Valley from the Bolt Creek fire, which then heads south over Seattle.   Purple colors indicate truly bad air quality.   Red is just bad.    The plume is relatively narrow...head east or west and you can get out of it.


The Puget Sound Clean Air Agency has a ceilometer in Marysville that shows the vertical structure of the smoke plume at that site (which is a bit north of the worst of it).  The graphic (shown below) shows that the worst of it (yellow colors) was down low and moved in last evening.  Yuk.

The latest high-resolution visible satellite image around 7:30 AM really shows the smoke from the Bolt Creek fire exiting the Skykomish Valley and spreading out over northwestern WA:


So what is going on and when will it stop?

The Bolt Creek fire is really not spreading but is smoldering in the interior.  This has gotten worse during the past few days as temperatures have risen and relative humidities have plummeted.   

Here is a plot of the relative humdity and moisture content of small dead fuels at the nearby Johnson Ridge RAWS site.  Yesterday, relative humidity dropped to around 10% and fuel moisture to roughly 6 %.

These are favorable conditions for fire.



The fire-favorable conditions have been driven by easterly (from the east) flow that unforunately pushes smoke into western Washington as well.

And the clear skies aloft and longer nights allow cooler/smoky air to settle into lower elevations and not mix vertically.   That is why conditions worse overnight.

But there is good news ahead.  Solar heating today should help mix the smoke through a larger volume of air reducing surface smoke concentrations.

Tonight, the pressure difference across the mountains will reverse, and cooler ocean air will move into the west.

Smoke time will be over for western Washington.  Unfortunately, that is not good news for the eastern slopes of the Cascades.

To illustrate, here are the near-surface smoke forecasts (from the NOAA HRRR smoke system) for this morning and tomorrow morning.  Good for Seattle, bad for Leavenworth.



So if you are sensitive to smoke and leave in Puget Sound.....wait a few hours before taking that walk or run.  If you are living in east Washington....you better get your exercise in today....



Comments

Post a Comment

Popular posts from this blog

Why so little lightning in the Pacific Northwest? And a very nice weekend ahead.

Image
During the past 24-hours, there have been a few lightning strokes over the region (see below) but nothing to write home about (see below). It turns out that the Pacific Northwest and the remainder of the West Coast have some of the lowest frequencies of thunderstorms in the entire country (see below). But why?    My podcast provides the answer. And I also give the weekend forecast....and I think most will like what I have to say. To listen to my podcast, use the link below or access it through your favorite podcast service. Some major podcast servers:     Like the podcast? Support on Patreon 
Read more

The Time of Year You Can See the Air Move

Image
  Most of the time, you can not see the air move.   You can feel it, but the complex, turbulent motions are invisible to you, except when it interacts with leaves and branches on trees and plants. But for a few weeks of the year, the sky is full of small, cotton-like tuffs that like a natural MRI machine reveals the complex three-dimensional motions of the atmosphere.   Cottonwood season.  And we right in the middle of it.   Being cottonwood aware is of particular value this year.  It reveals the active dispersion and movement of air that makes the outdoors essentially COVID safe, and thus should be of some comfort for those nervous about transmission outside. Cottonwood seeds are embedded in small cotton-like fibers.   A million seeds weigh about 3 pounds.  Yes, each seed and tuff weights about .000003 pounds.   And that fact, plus the cottonwood tuff, means that these seeds fall VERY, VERY, VERY slowly.   So slowly that they are excellent markers for the three-dimensional flow of the
Read more

A Much Colder Than Normal April: But How Unusual?

Image
  April was a chilly month over the Northwest, but how chilly?     It turns out the answer depends on where you are located. The difference between this April's temperatures from normal across Washington State (below) shows that the entire state was well below normal.  The eastern side of the state was particularly frigid:  some areas were more than 6 degrees below normal.   Considering the west side of the state, the April mean temperatures at SeaTac Airport are plotted below.   This April was the coolest since 2011. April 2020 was in 15th place for the coolest April since the mid-1940s and was a bit more than 4F below normal.  So if you felt that you were cheated out of normal spring warmth...you are right. But if you really wanted to experience extraordinary April cold you had to be east of the Cascade crest. Consider Yakima.  Wow.  It had the third coldest April temperature since the mid-1940s.   And the all-time record in 1955 was only slightly colder. If you want a longer-te
Read more