One of the harshest days in western Washington history….and why the lowlands are protected from surface smoke

Yesterday (Sunday), was one of the most extreme high-temperature days in Western Washington history.

In some ways, almost equal to the June 2021 heatwave.

Review the map of Sunday’s high temperatures (below, click image to expand). 88F at Sea Tac and lower than 90 in some locations.

Great for mid-October.

As noted in my previous blogs, this heat is related to strong winter winds (from the east) that warm in compression as they move into western Washington.

Now let me convince you how unusual this is. Consider Paine Fields in Everett. At this station, temperatures hit 87F – the warmest October day on record at that location. Runner-up is the cooler 4F. SeaTac had the second warmest day on record, with the warmest being October 1.

October profile

But let me impress you even more.

During the June 2021 heatwave…largest in Northwest history… SeaTac Airport rose to 108F, 17F above the previous record high for the day. On Sunday, the SeaTac hit 88F, 16F above the previous record of the day.

In Everett, a peak of 87F on Sunday was 29F above the typical high for that day, while on June 28, a 100F temperature was 31F above the normal high.

Bottom line: yesterday was extremely rare.

Smoke protection

Today, a lot of smoke flies overhead but the air quality is pretty low.

Why?

To show the smoke, here’s a satellite image visible around midday. It looks like something from Dante’s Inferno! Later satellite images look similar.

But the air quality map at around 6:7pm shows good air quality around Puget Sound, with the worst conditions around Olympia (expected due to many rooms filled with smoke).

It turns out that something is protecting us from living at lower altitudes, preventing smoke from mixing to the surface.

Our friend’s name? Reversal.

An inversion occurs then the temperature warms with altitude. The inversion prevents mixing.

Why do we have an inverse? Because the cool sea air at the lower level moves through the night, while the warm air stays high up.

That creates an inverse.

This is a graph of the temperature (red line) and dew point (blue dash) from the launch of the spherical weather station (radiosonde) at Forks on the WA coast around 5pm this afternoon. Approximately 5000 ft of temperature increases with altitude. It’s the reverse!

The reversal will be weak but still in place on Tuesday, so I expect our air to remain breathable.