Smoke Has Caused Temperature Forecasts to Go Crazy Plus An Update


Have you taken a look at the temperature forecasts on your favorite smartphone app or online service?

Most are predicting temperatures that are crazy warm by as much as 15-20F!
Yet, the National Weather Service forecasts are reasonable. Why?

Before I explain, let’s review what is going on right now.

The latest satellite image shows an area of deeper smoke has moved northward over western Washington.  Smoke has also moved into eastern Washington.  Only the north Cascades is in the clear.

At low levels, marine air and low cloud have pushed into portions of western Washington.  With more smoke aloft, solar radiation will decline over western Washington today, providing an infernal murk that is a bit depressing.

The current air quality situation is similar to yesterday afternoon with unhealthy conditions over the region and very unhealthy particulate levels at some coastal locations and the Willamette Valley.  Hazardous condition are found in the Willamette Valley and northern Oregon.   This is bad folks.

The good news for Puget Sound residents is that conditions have improved a bit over the past several hours (see plot):  small particle concentrations (PM2.5) declining from around 170 to 130 at Beacon Hill in Seattle.  I would avoid heavy exercise today, even if you are young and healthy.

I do have good news.  The end is in sight for suffering residents of western Washington.  But you have to get through today.

The latest NOAA/NWS HRRR forecasts for 4 PM today suggest that there will be only slight improvement today over western Washington (we remain in the darker red–over 100 micrograms per cubic meter of the small particles).  Portland remains terrible and conditions are very poor east of the Cascade crest.

But increasing onshore flow on Sunday really will initiate a transition.  MUCH cleaner air will push in by 4 PM Sunday over the coastal zone and will just reach Seattle late in the afternoon.

By 1 AM Monday, air quality will be hugely better in western Washington and the Willamette Valley, but those living east of the Cascade crest will be remain in the murk. Northern Idaho and western Montana as well.

Smoke causes surface cooling and ruins automated forecasts

The wildfire smokes has a profound impact on surface temperature, causing cooling by reflecting the sun’s rays back to space and absorbing some of it aloft.  That is probably obvious to most of you from being outside yesterday, but consider the radiation measurements on the roof of my building at the UW (see top panel below).  Much less radiation yesterday (a drop of 22% from 19.83 to 15.49).

The temperature plot is shown right below– highs dropping from 95 to 73.

Now here is the problem.  Most weather prediction systems are not including smoke and thus are missing its profound cooling effect.  Thus, their forecasts are too warm–and too warm by as much as 20F in areas of dense smoke.  On my smartphone right now, Portland is predicted to get to 79F and Eugene, OR to 82F.   In truth, they won’t get out of the 60s. These forecasts are coming from

The automated services are all too warm because the modeling systems on which they are based do not include smoke.     That is also true of many of the National Weather Service models.  The NOAA/NWS HRRR smoke modeling system is still experimental and will go operational this year.  And I expect all modeling systems will include smoke within the next few years.

This situation shows why it is good we have skillful human forecasters minding the shop at the National Weather Service:  they are manually correcting the model predictions so that accurate forecasts are still available.


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