Wednesday, November 4, 2009

Stress-free Weather/A Note on Atmospheric Thickness

November 4, 2009
8:45 P.M.
I'm sorry I haven't made a forecast more recently... it's just because I've had so much work lately and other stuff in general. My life has been hectic.
With me, weather and stress are inverses of each other. Most people would find their stress relieved by a light drizzle or sunny skies. Nothing takes away my troubles like a fierce windstorm, major flooding, or a blizzard that buries the entire city under 20 inches of snow. Perhaps the rather benign weather as of late has added up to it all. It probably has. However, try using that as an excuse for a poor score on a test. And with the forecast up ahead, it looks like it will all even out. :)

Shown above is a diagram of the 1000-500mb thickness. This model shows the isobars of pressure in the area (note the HUGE 946 mb low in the Gulf of Alaska!) as lines, and the thickness in the atmosphere between the 1000mb and 500mb levels as different colors. The thickness means the physical distance (usually in meters) between the parts of the atmosphere where pressures of 1000 mb (around sea level) and 500 mb (around 18,000 feet). In tropical regions, increased water vapor and temperature make the thickness larger, while the thickness is smaller in polar regions. You can see arctic air/very small thicknesses in the top right hand corner of the model.

Anyway, that low pressure center is very low - about the pressure of a category 4 hurricane - and it will create some inclement weather for us. First and foremost will be waves. 30 foot high swells originating from the intense winds surrounding the low center will hit Washington, starting Thursday and peaking Friday night. Large swells need time to form, an area to form on, and winds to drive them, so this system will be very conductive at producing very large waves.

Next, let's talk about wind. Look at this diagram above. Look at those winds! While they might not be as strong as those found in a hurricane, they cover a huge area, practically the whole northeastern Pacific, with a swath of particularly strong winds SW of the low. These winds will not hit us in their full force but we will see some wind tomorrow, with gusts topping out at around 50 on the coast and north interior and 40 in the Puget Sound basin. Nothing too serious, but definitely noticeable. The lake should be nice and choppy.

In addition, we should get a lot of rain. Right now it is looking like 3 to possible 5 inches in spots in the mountains and an inch or so in the lowlands. There shouldn't be any major flooding, but most rivers should rise significantly, and the Nooksack and Skokomish Rivers have Flood Watches posted for possible flooding.
Looks like tomorrow will be a stress-free day. :)
Have a good one,

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