Today, a quick lesson about the wacky weather patterns of the Puget Sound area, brought to you by our friend the Puget Sound Convergence Zone.
What is the Convergence Zone, you ask? Well, in short, the Puget Sound region is fascinating topographically. Not only do we have a big body of salt water (Puget Sound) snaking East and South through the region for about 80 miles, but we also are flanked by two mountain ranges: The Olympics to the West, and the Cascades to the East. (Metro areas in yellow on the map below)
The Olympics play a major role in the Convergence Zone. Winds coming from the NW are split by the Olympic mountains, forced to go North and South. Part of the airstream flows East down the Strait of Juan de Fuca (big body of water North of the Olympics in the map above) and the other half travels around the bottom of the Olympic range. When the Northern flow hits the I-5 corridor (where most of us live) and the Cascade mountains, it is forced South. The same happens to the Southerly flow, but it is forced Northward. And then this happens:
The split weather patterns normally converge (get it?) somewhere North of Seattle (between 8 and 16 miles), and when they meet convection occurs–which normally causes storm cloud development.
Combine that with changes in altitude (lots of people live East, in the Cascade foothills), big bodies of salt water (which remain at a fairly consistent temperature year-round and create a local microclimate for downtown Seattle), and you get wacky weather. Today is a great example thereof. Here I sit at my office, which is nearly at sea level in downtown Seattle. Looks like just another gray day, right?
And yet, here is a street scene from the town of Edmonds, ~12 miles North (and definitely in the Convergence Zone today!):
This is the first snowfall of the 2012-13 Winter–ironically hitting us in the first 3 days of Spring.
So the next time you hear someone say, “Ugh, I could never live in Seattle–it’s just gray and rainy all the time”, you’ll know there’s far more to it than that! (And/or you stopped reading long ago and will simply agree with them.)
UPDATE–5:00PM: It’s now beautifully clear, sunny, and 51 degrees outside. I drove back to work from a meeting with my sunroof open. That’s Seattle in Springtime for you!