Western Washington Smoke: Darkest Before the Dawn

Ash was falling last night around Puget Sound, with white flakes apparent on many cars.  And air quality is terrible right now, about as bad as it has been during the entire extended event.

But relief is close at hand, with dramatic improvement guaranteed tonight and tomorrow.

Why so bad now? 

Because we have had a conduit of lower-atmosphere winds from the fires over the North Cascades and southern BC, directly into the Puget Sound region.  A perfect set up air quality degradation here.  You can see the plume of smoke in the latest visible satellite imagery:

And it more that obvious in the forecast smoke concentration for 8 AM from the NOAA/NWS HRRR smoke plot.  Apocalyptic.  The vision of Smokezilla.

The small particle concentrations (PM2.5) measured at Seattle (Dwamish) and north Seattle (Lake Forest Park) illustrates the sustained high values and they have been rising overnight to about 150 micrograms per cubic meter.  These are unhealthy levels and twice those being observed in Beijing right now. 

An issue that has not been discussed is the effects on our temperatures.   The dense smoke has greatly reduced solar radiation reaching the surface.   Although yesterday still got to around 90F in our area, without the smoke, temperatures probably would have surged to the mid to upper 90s. 

But the most interesting issue is our LOW temperatures.  Notice how warm it has been at night?   To illustrate, here is a plot of the temperatures at SeaTac Airport for the last 4 weeks, with normal highs and lows plotted.  Notice how our low temperatures have been crazy warm the last two days?  (see the dashed oval).  Like 10F above normal.  That is due to the smoke layer, which acts as a blanket, reducing the ability of the surface to lose heat to space through infrared radiation.

Now the good news.  The end (of the smoke) is near.   The easterly flow above the Cascades has weakened, reducing the smoke supply.  And later today onshore flow should rev up, bringing in cooler, cleaner marine air. 

Here is the HRRR smoke forecast for 5 AM tomorrow morning.  Clean air (white) is moving inland and is about to reach Seattle.  Not good for eastern Washington and Idaho since the smoke will be blown eastward.  And increasing winds could stoke the fires.

Finally, I am working on two future blogs on the wildfire issue, something that I have become very interested in.  The first will describe how our smoke is not a "new normal" but a return to the "old normal" (there were far more fires and smoke during the early 20th century and before). 

The second will talk about the cause of this situation, with the key issue not being climate change (which does contribute) but our mismanagement of our forests, nearly a century of fire suppression, human intrusion into wildlands, and flammable invasive species.  And I will suggest that there is a real opportunity for a bipartisan, non-political effort to fix our forests.



from Cliff Mass Weather and Climate Blog https://ift.tt/2nYsDA7