Monday, August 1st, 2011
When people think of Seattle, they probably think of coffee, bad sports teams, and people with webbed feet. They probably don’t think of air conditioning. However, we can get pretty hot in the summer. I remember a couple years back at Sea-Tac when the mercury hit 103 degrees. Why do people not have air conditioning then?
Because mother nature gives it to us for free!
Right now we are in a very typical summer weather pattern, with a big high pressure zone off of our coast blocking systems and occasional onshore flow preventing us from getting too hot by continually flushing out our air with cooler air off of the Pacific. First, fog forms on the coast in the morning as the moist air from the previous night cools off and condenses, as cool air can hold less moisture than warm air. Due to differences in heat capacity, the land heats up faster than the ocean, creating local pressure differences, with higher pressure over the sea and lower pressure over the warmer air on land. This creates a “sea breeze,” with air flowing from the ocean to the land, as the atmosphere is always trying to balance itself out. For those of you who have taken physics, this is defined as entropy, and is stated in the Second Law of Thermodynamics. The breeze strengthens throughout the day as the temperature differences increase, and subsides after midnight. Still, there is relatively lower pressure in the rest of Western Washington, so this marine air marches on in, kicking out any any air from the previous day. As the temperature cools off, the moisture condenses to form low stratiform clouds and fog on occasion. As the sun comes back up, the clouds “burn off” due to the warming of the atmosphere and the ability of the air to hold more water vapor. Meanwhile, the sea breeze machine on the coast gets going once more, and the process repeats itself.
If that seems confusing, check this article out: http://www.komonews.com/weather/faq/4306832.html
It explains it in more detail and has diagrams to show you. I didn’t want to steal any diagrams off KOMO’s page.
I was on the deathly slow internet found on BC Ferries and this was all I could manage in an hour. Maybe I’ll write another post tonight at my hotel in Victoria.
Thanks for reading!