Similar Forecast, and Variations in Temperature and Precipitation

Thursday, September 29, 2011
9:47 P.M.

There isn’t much to talk about weatherwise… the models are still forecasting a warm day today with highs in the low to mid 70s and mostly sunny skies, with nice conditions Friday as well. We will see a weak system blow on through on Saturday, with cooler conditions Sunday. Next week looks cool and wet, but the models differ on details. I will let you know more as next week approaches.

One thing unique about the weather of Washington is that we can see vast variations in temperature and precipitation over short distances. Much of this has to do with our local topography. Places like Florida are essentially flat, and do not experience much variation with temperature or precipitation due to topography. Meanwhile, Washington has a moderating ocean, two major mountain ranges, an inland sea, rainforests averaging over 200 inches of rain each year, and then places like Sequim some 45 miles northeast, averaging 15 inches per year. If you want to get really dry, head over to the Tri-Cities.

 

One thing that has always fascinated me, though, is the differences in temperature right around the Seattle metropolitan area. Why is it that the coldest Seattle usually gets at night during an arctic outbreak is in the high teens, while suburbs may dip below 0?

The answer, of course, is the urban heat island. Although the picture below isn’t the best example, it does the job. The heat island is generally most pronounced during arctic outbreaks in the winter at night, but it can be observed at any time of the year.

You can see warmer temperatures in places where there are buildings, and much cooler temperatures by the coast and across the sound/near Lake Sammamish. Downtown Seattle and the industrial sector east of the Duwamish are the hottest areas, with other cities and industrial areas being hot as well. Another pronounced site is Renton, where one of the Boeing factories resides.

I wish I could find a better picture during an arctic outbreak, but that will have to wait for another time. And I apologize if this post feels like it was written poorly, because I am trying to beat the clock to catch my atmospheric sciences class.

Thanks for reading!
Charlie

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