A Super Inversion is Over Western Washington

This morning, temperatures were in the lower to mid-40s over much of western Washington; but ascend  to 1500 ft and mid to upper 60s are occurring.  Huge increase of temperature with height....a super inversion.

Below the inversion, the air has become saturated, with lots of fog.   The view from the Seattle SpaceNeedle panocam shows a dramatic, and very beautiful, scene:

But the surface view from North Seattle is one of fairly dense fog.

How strong is the inversion?  Let me tell you...and be prepared to be impressed. 

Here are the temperatures above north Seattle from the regional profiler, a sophisticated device that can measure temperature aloft by tracking sound waves (the speed of sound depends on temperature).    Temperatures are in C and range from 10C (50F) to about 22C (72F), 700 meters above the surface.  Most of the change is in the lower 300 meters (about 1000 ft)

The radiosonde-based temperature profile at Quillayute on the Washington coast shows a similar structure (red line below), with about a 17C (30F) increase in temperature within a very thin layer near the surface.  The blue dashed line is dew point...indicating saturation near the surface (with fog)--the temperature and dew point are the same.  But aloft, the temperature and dew point separate, indicating very dry air aloft.  Dry and warm.

 Why such a super inversion?     We start with a big ridge of high pressure overhead (see upper level map for 5 AM this morning).

As a result, there are virtually no clouds aloft, which allows the surface to radiate infrared energy to space, causing surface cooling.  Nights are long now--also good for cooling!

But there is more.  A big high pressure area is associated with sinking air aloft, but less sinking near the surface (air can't pass through the surface).    Sinking causes air to be compressed (pressure increases towards the ground) and compressing air warms it up (think about how warm your bike pump is after use).

So with more sinking aloft than at the surface, the high is preferentially warming aloft compared to the surface---this helps build the inversion.

And if you like subtleties there is more.  At the surface, the highest pressures of the region are east of the Cascades, causing some easterly flow aloft. 

To show this, here are the winds and temperatures above Sea Tac Airport for the past day (time increases to the left, height is in pressure, 850=5000ft).   The wind barbs show easterly flow (from the east), which descends over the western slopes of the Cascades producing MORE compressional warming aloft. 

Good for the inversion.  In fact, look at the temperatures on the chart...there is a big increase from the surface to roughly 930 hPa pressure (about 800 meters above sea level.)

The fog will burn out in a few hours and warmer air should mix down to the surface, giving a fine day in the 60s. 

But if you can't wait to warm up, put on your hiking shoes and head up a local foothill.  You will start with a jacket and end up in a tee shirt...guaranteed.

from Cliff Mass Weather and Climate Blog http://ift.tt/2xvtfAq