High Pressure, Inversions, and Fog

Tuesday, November 29, 2011
10:59 P.M.

Photo Credit: Kevin Ebi @ Living Wilderness
The next week or beyond will be very boring and uneventful for meteorologists. The culprit? A HUGE ridge of high pressure off the Eastern Pacific.
Take a look at the current atmospheric configuration from tonight’s 00z UW WRF-GFS run.
Valid 10:00 pm PST Tue, 29 Nov 2011 – 6hr Fcst – UW 00z 36km WRF-GFS 1000-500mb thickness, SLP
There is a very, very strong ridge of high pressure over the Eastern Pacific. We have a weak system pushing through right now, but after that system passes through, we will be very dry, as this ridge will push the jet stream up north into Alaska, preventing any storms from reaching our area. Additionally, with light gradients over our area, cool, dense air will sink down to the surface and create an inversion, which is where the air at the surface is colder than the air aloft.
Inversions are very stable, and do not mix up the atmosphere much. Due to this lack of mixing, we often get fog and smog, as pollution gets trapped in the inversion over our area. People with asthma should be careful in the coming week, as they may encounter respiratory problems. People may also need to limit exercise or strenuous activity outside, as the air may irritate the lungs and make it hard to breathe.
This ridge ain’t going anywhere. The extended WRF-GFS model at the UW goes out to 180 hours, and the ridge is still there and is stronger than ever.
Valid 10:00 pm PST Tue, 29 Nov 2011 – 6hr Fcst – UW 00z 36km WRF-GFS 1000-500mb thickness, SLP
While we are relatively warm aloft and cool at the surface, areas east of us will see numerous arctic outbreaks due to a huge trough in the jet stream. If this high was further west, we could be talking about some arctic air for our region. Alas, it is too far east. The plains should be very cold at times this coming week.
If you want to escape the haze, fog, and smog associated with this inversion, head into the mountains! The air will be warmer and cleaner. You’ll look down at the Puget Sound lowlands and think “Was I really breathing that?” Inversions are gross… they indicate lame weather for us meteorology nuts while suffocating us all in dirty air. These inversions used to kill… the London smogs are a great example. Since then, people have burned cleaner materials (ex: natural gas as opposed to wood-burning stoves) and inversions now are much “cleaner” than they used to be in most places. Nevertheless, I’m not a fan.
Thanks for reading!
Charlie 
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