Wednesday, October 19, 2011
Yesterday, I wrote about the variability of autumn weather in the Pacific Northwest and how we can see big changes in short periods of time. Today, we didn’t see a monumental change in the weather, but it definitely wasn’t like yesterday. As I was walking back from the IMA at the University of Washington, there was a nice, refreshing breeze and plenty of leaves flying around. It wasn’t super windy, but it was nice to feel some gusts ruffle my hair and send leaves in those small little whirlpools we often see in blustery conditions.
This diagram above shows the change in winds over the past 12 hours for different heights in the atmosphere as recorded by the Sandy Point profiler. The change is not quite as dramatic as yesterday, but you can still see a shift from northerly winds to southerly winds in the lowest levels of the atmosphere. You can also see a change in the winds in the upper atmosphere from southeasterly to south-southwesterly, which generally means that a low pressure system is progressing westward. We had a weak low pressure system give us some clouds today, but we will see stronger systems Friday through the weekend.
These systems will be directed to us via a zonal jet stream pointed right at us. Check out the graphic below… it shows the winds at the 300mb level forecast for 8 P.M. PDT Friday.