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The Unique Weather of the Puget Sound

19 Oct 2017, 4:39 pm

Listen up, nerds, today we are exploring a little weather phenomena unique to the Puget Sound.

Geography

For starters, we gotta talk geography.

The Puget Sound is a body of water nestled in the far northwestern reaches of the contiguous U.S.
Next to the Pacific Ocean, the Sound is protected by one of the coolest bits of land in the world– the Olympic Peninsula.

The Olympic Peninsula is home to Olympic National Park and if you haven’t been, I highly suggest it.
Rugged coast, Lush rainforest, and towering snow-capped peaks.

On the eastern side of the Sound lies the Northern Cascades. A rugged collection of jagged peaks and glaciers lost to the Americans East of the Rockies.
This underappreciated range is the snowiest place in the lower 48.

The Puget Sound itself is a salt-water inlet of the Pacific Ocean. It boasts a plethora of islands and an abundance of marine life any zoo-goer only dreams of seeing in the wild.

Needless to say, you should start planning your next vacation now. (pro tip: go for the summer months for your best shot at seeing some sun)

Climate

Ask anyone, I don’t care where he/she might live, and he/she will tell you that the Northwest is rainy. So rainy, in fact, that the entirety of the region is miserable.

For starters, that person is wrong.
Portland, OR in an average year only sees 13 fewer days of sunlight than the Minneapolis, MN metro!

Second, Seattle sees about 37.5″ of rain each year while New York City sees a whopping 45″ of rain each year. (Of course melting the snow for the water equivalent)

So now that we’ve cleared up its bad name, let’s talk the big picture.

Summers are typically dry. The Northwest can go months on end with little or no moisture.
But winters are a different story. From late September to June, the rain hits. And though it’s typically lighter rain, all of that geography we discussed earlier plays a big role in where that rain goes!

Rain Shadow

A rain shadow is a pretty cool weather phenomena. We often talk about orographic precipitation. Just a really fancy way of saying the mountains wring the moisture out of clouds.
Well, once those higher elevations squeeze the moisture from the clouds– they don’t have much left to give. Which means, many areas downwind of mountains or large hills sometimes remain dry.

The almost 8,000 foot peaks of the Olympic Peninsula are a great example of this phenomena. The high peaks wring the moisture out of incoming storms, and portions of the Puget Sound wind up extremely dry– even during the rainy season!

Check out this neat radar loop made by Meteorologist Andy Stein showing the rain shadow:

Olympic Rain Shadow

Check out the rain shadow created by the mountains of the Olympic Peninsula!

Posted by Meteorologist Jeremy LaGoo on Thursday, October 19, 2017

If you’ve ever made it through the San Juan islands, you’ve probably seen what this does to some of the islands!
Check out this shot I took of one of the dry islands last spring.

Convergence Storms

Now, all of that geography plays the opposite role as well! Sorta.

Those mountains create a convergence zone. The moist atmosphere has the water content, and the mountains act to funnel the wind together. This is known as convergence.
As the winds come together they have to go somewhere and the only way left is up! So the rising produces showers and even heavy localized storms!

Check out this example from the national weather service from just the other day!

We’ll call it good after that. Glad we all got to explore one of my favorite regions of the U.S. together!

For WeatherNation — Meteorologist Jeremy LaGoo

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