Another Surge of Wildfire Smoke Hits Puget Sound: The Worst on Record

Folks were surprised how quickly the air quality deteriorated Sunday afternoon, rapidly going from moderate air quality to unhealthy conditions with a profound loss of visibility.     Things improved over night around Seattle, but then went downhill today--with the worst hourly smoke levels on record (back several decades).

Let me show you and explain the fascinating and complex situation we are in.

Here is a plot of the particulate levels (PM2.5) at the Puget Sound Clean Air Agency Duwamish site from last Tuesday to 3 PM today (Monday).   You can see the rapid surge of smoke yesterday afternoon, followed by a sudden fall in yesterday evening.  And then it started rising again this morning, reaching a peak now that is far higher that either yesterday or last week.

In fact, this hourly smoke level is the highest on record at this site (going back roughly two decades) and higher than anything last summer--the plot below is the proof!

Yesterday, as the winds aloft turned northerly and northeasterly, the huge reservoir of smoke in British Columbia and eastern Washington surged southward overhead, but air quality did not decline immediately.

As the surface warmed, the lower atmosphere started to mix, higher and higher, eventually tapping the smoke aloft and bringing it down to the surface.  That is what caused the air quality to rapidly degrade.

Last night, the surface cooled,  the mixing driven by surface heating dropped off, and the lower atmosphere became stable, with little vertical mixing.  So we stopped tapping the smoke aloft.   Then relatively clean air moved into central and northern Puget Sound from the Strait of Juan de Fuca, leaving us with better quality air, which was present this AM.

But why did things get so bad this afternoon?   For one thing, the surface started to warm, resulting in more mixing of smoke down to the surface.   The noon MODIS satellite imagery clearly showed smoke above the region and particularly Puget Sound.  Eastern WA looks like something out of Dante's Inferno.

But look really closely.  You can see smoke plumes over the eastern slopes of the North Cascades, with the smoke moving toward Puget Sound.

The 3:40 PM satellite image from the NOAA GOES satellite shosw the smoke from these fires crossing the Cascades and reaching Puget Sound. Some domestic smoke.  A source of primo smoke aloft.

As illustrated by the EPA AirNow graphic, although it is smoky over Puget Sound, it is crazy bad in Port Townsend and Port Angeles, as well as areas along the eastern slopes of the North Cascades where the numbers are in the 200s.   Extraordinarily unhealthy.

What about the future?   Let's check out the NOAA HRRR smoke forecasts, which have proven to be stunningly good. Tomorrow, the winds become increasingly easterly, which means eastern WA smoke will be coming right into us (see forecast for 3 PM tomorrow).  Not much better than today.

Wednesday is the transition day, with a onshore, marine push beginning that evening.  Thursday, should be a MUCH better day, with clean ocean air over our region.

On a lighter note, the Puget Sound Clean Air Agency gives advice on what you should do in this smoky situation.  The only thing advisable is to work on your laptop!

from Cliff Mass Weather and Climate Blog https://ift.tt/2PmpkiN