June 2, 2011
Hello everybody, I'm at the Garfield Community Center right now and for some odd reason I can't post pictures to my blog at this time. Anyways, I have some good news! Next weekend will be our warmest weekend since September! Don't get too excited, we aren't getting into the 90s. However, we will warm up to approximately 75 on Saturday and possibly even higher on Sunday. I would not be surpised if Seattle hit 80 on Sunday, although it seems like the National Weather Service and the tv stations are calling for mid to upper 70s with a few isolated 80s near the water.
Why are we all the sudden getting so warm when we have been so cold lately? It all depends on which direction the wind flowing into our area is coming from. For nearly all of this spring, we have had an onshore flow, which means that air is flowing "onshore" into our area from the Pacific. This type of weather generally gives us cool temperatures with scattered showers. The offshore flow typically ramps up at night, because as the land warms during the day, it decreases in pressure, and air rushes in off the Pacific to fill the discrepancy in air pressure later in the day through the night. We have seen lots of stratus clouds in our area in the morning, and these are a result of the "marine push" from the ocean. Because of their maritime origins, stratus and other low-lying stratiform clouds are known as the "marine layer" by local meteorologists.
This weekend though, we will have an offshore flow, which will warm us up significantly. When air is coming off the Cascades, it has continental origins (warmer at this time of year) and it also warms up as it descends. We get this offshore flow when we have lower pressure off the coast and higher pressure inland, since air always flows from low to high pressure.
We will get very warm on Saturday, but why don't we immediately get a marine push on Sunday? The reason is that the flow will stay offshore. Although the land will have lower pressure because it has warmed up, the pressure over the ocean will still be lower, due to the pressure gradient from a ridge of high pressure over the area, a weak area of low pressure off the coast, or a combination of the two.
However, all good things must come to an end, and we will get a marine push Sunday night into Monday just in time for the last few remaining days of school for us seniors. This is because the flow will turn onshore, with higher pressure over the water and lower pressure over land. This marine push is a very common occurence during the summer, and it is the principal reason why we don't need air conditioning in the Pacific Northwest (although it would have been nice a few years ago when Sea-Tac got up to 103). Open your windows Sunday night and see how the house feels Monday morning.
Thanks for reading! Off to a gig...