Cliff Mass: Seattle’s worst 24-hour air quality on record

Desdemona Despair

By Cliff Mass
15 August 2018

(Cliff Mass Weather and Climate Blog) – Air quality in western Washington is very poor right now.

Incredibly, in central Puget Sound it is probably the worst in the nearly two-decade observing record of the Puget Sound Clean Air Agency for any time of the year.

I have been here a long time and I have never seen anything this bad.  The view from the Seattle SpaceNeedle Panocam is murky.

And the view from my department is very limited … no mountains and can’t even see across the Lake.

But now, let me really impress (or depress) you.  Below is a plot of 24-h average particulate concentration (PM2.5) in the atmosphere at the Puget Sound Clean Air Agency Duwamish site in Seattle.  The past 24-h was the worst on record for any time of the year.  Number two was the smoky period last summer. […]

So why did our near surface air quality get so bad so fast?

Fires were burning for quite a few weeks in British Columbia, California, and eastern Washington, but western Washington had clean air at low levels (off the Pacific) with smoke aloft.  But on Monday, surface high pressure started to build in north and east of us (see map), resulting in easterly and northeasterly flow over the Cascades that brought the smoke over and down the terrain into western WA–allowing smoke to get to the surface. [more]

Seattle’s Worst 24h Air Quality on Record