Super Inversion

Normally, temperature decreases with height, and for good reason.  

The sun's rays warm the surface more than the atmosphere above; thus, air temperature tends to decline with elevation.

But sometimes the opposite occurs: temperatures are cool near the surface, and warm air is found aloft.

Since this is the opposite of the normal situation, we call it an inversion.

Most of the time, low-level inversions are weak, with temperatures increasing by only a few degrees above the surface before falling aloft.

This week was something else. 

 A SUPERINVERSION formed, with temperatures increasing by about 20°F within the lowest few thousand feet.

Unbelievable.

Over SeaTac Airport this morning, temperature was around 48F near the surface and around 70F at 1800 ft.   

22F warmer!  Amazing. 

At Forks, along the WA coast, temperature increased from 8 to 22°C over a similar distance in the vertical (see below), 

What is 25F!!!    Wow.

Looking at the surface weather map, showing the lowest temperature this morning around the I-90 corridor from Issaquah to North Bend, indicates a temperature range from 65 at higher elevations to 40 F at lower elevations, such as near Carnation.

Why such an amazing inversion this morning?   

The skies were generally clear, allowing the surface to cool off by emitting infrared radiation to space.  Nights are getting longer as well, allowing more time for cooling

Furthermore, there is a strong ridge of high pressure overhead (see below),

which not only produces the clear skies, but also forces sinking motion aloft that warms aloft by compression.

The inversion weakened greatly during the day as solar radiation warmed the surface.  

And with the ridge of high pressure aloft moving east, the sinking air that supports this crazy temperature structure will soon be history.