Anacortes Washington Weather Station Provided by Mt Erie Fire Department

Weather Essays

The following weather essays are weather columns written by weather columnist Vince Streano for the Anacortes American. You can read his current column by clicking here, and then going to the “Weather or Not” column.

Banana Belt or Rain Shadow?
Copyright Vince Streano, 1999

Nestled within the Olympic rain shadow, just west of the Cascade mountain range, Anacortes enjoys unusually mild weather for a community that shares its latitude with Newfoundland. Described by many as the banana belt of Western Washington, the area has mild winters, an exceptionally long spring, and summers that end too soon. Since I haven't seen a banana tree since moving here, I prefer to describe our weather as mild because of the influence of the Olympic rain shadow.

When my wife and I moved here in March of 1989 from Southern California, we were gloriously ignorant to the sudden mood swings our weather can exhibit. In Southern California the weather is extremely predictable, bordering on boring. The rainy season is from November to March, and it's sunny and warm the rest of the time. Before we moved our friends kept asking how can you move to someplace where it rains all the time?
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First Snow Fall
Copyright Vince Streano, 2005

So, there I was Thursday morning, the first day of December, waiting for the first snowflakes to fall like a kid waiting for Santa to drop down the chimney. The National Weather Service had predicted snow for late in the afternoon, but I was hoping it would come earlier, so I could take pictures. By 10 AM the skies to the north were almost black. Overhead the clouds were heavy with moisture and the color of pewter. I checked the radar and could see the beginnings of snow falling to the north and west of Fidalgo Island.

Just after 10:30 the first flakes began to fall. Tiny little flakes you could barely see. Gradually they got larger, and larger, until the flakes were the size of half dollars, floating gracefully to the ground. I was awestruck by the beauty of what I was seeing. I was afraid it might be a brief flurry with a sudden ending, but the snowfall kept getting heavier. My weather station said the temperature was 36 degrees, which explained why the flakes weren't yet sticking on the ground. After twenty minutes of what I would call heavy snowfall, I called the National Weather Service on the Weather Spotter hotline to report what I was seeing. They were surprised it was already snowing in our area. The forecaster asked me the temperature and the dew point, and thanked me for the update.
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Has this ever happened to you? You get in your car on a bright sunny morning for a drive to Seattle. The weather is great, and you're looking forward to an easy drive down I-5. As you progress south on the freeway, the weather ahead looks a little gray. Around Smokey Point the clouds begin to thicken. Then you get to Everett and the weather changes to a pounding rain. What happened? It's almost like you entered a parallel universe. Everything looks the same, except the weather. Then, about fifteen miles further down the road, the universe shifts back, the sun is shining, and everything is back to normal.

What happened is that you entered the dreaded Puget Sound Convergence Zone. Florida has its Hurricanes, Oklahoma has its Tornadoes, and we have our convergence zones. The PSCZ is the most consistent, and produces many fascinating weather phenomenon. I've often wondered how convergence zones are formed, and what causes them.

In doing some research, I discovered the PSCZ is formed when winds racing across the Pacific Ocean slam into the Olympic Peninsula, and are split in two. Half the wind flows around the peninsula to the South, and the other half goes north. Once the Southern flow hits the I-5 corridor, it turns north. When the Northern flow hits the corridor, it turns south. Now you have two very unstable air masses converging on each other. Think of two runaway freight trains, on the same track, racing towards one another.

When the trains collide, or in this case the two air masses, a tremendous amount of energy is released. This energy goes straight up into the atmosphere. The warm ground level air rushing upwards collides with the colder upper atmosphere, causing convection, which in most cases produces rain. The colder the air in the upper atmosphere, the more instability you get. If the convergence of the two air masses is unusually unstable, it can also produce hail, and in some cases snow. Because so much energy is expended at the point of collision, the areas on either side of the zone are usually calm, and in many cases remain sunny. Which is why you feel as if you're entering a parallel universe when you cross into the convergence zone.

The Puget Sound Convergence Zone is not always in the same place. It has been recorded as far North as Northern Skagit County, and as far south as Pierce County. The exact spot depends on the speed of the two colliding air masses. If the Northern branch is moving faster than the Southern flow, the zone will be formed further south, say around Edmonds. If, however, the Southern winds are moving quicker, the zone will shift northward, towards Everett.

Many factors must come into play before a convergence zone can be set up. You have to have two different air masses moving in the right direction, and at the correct speeds. It helps if the air temperature on the ground is warmer than the temperature in the upper atmosphere. And you have to have a convergence that expends enough energy to create instability. So the next time you're headed down I-5, and you think you suddenly entered the twilight zone, you now know it's the convergence zone. Doo doo doo doo.

Keeping weather statistics is both a curse and a joy. A curse because you have to be compulsive about faithfully entering the records at the end of each day. If I take a trip, I have to find someone I can trust to record the records for me until my return. It's a joy when I can look back over the records and begin to discern patterns and anomalies that crop up throughout the years.

As we begin our summer season I thought it might be interesting to go back through my records and try to predict when it might be sunny and when it might rain, based on my records for the past five years. I was surprised at a number of facts I discovered while doing my research.
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I was walking around downtown Anacortes the other day in a pouring rainstorm. Suddenly it dawned on me. No one was carrying an umbrella! Over the next couple of days whenever I went to town in the rain, which was most days, I did a mental umbrella survey. I still haven't seen one. What is it with Anacortes residents disdain for the bumbershoot? Personally I don't carry one either. Usually the rain isn't that hard, and a hat and jacket keeps me relatively dry. But lately it's been raining cats and dogs, and still no umbrellas. Maybe it's a macho thing. Are Anacortes residents too tough for umbrellas?

Since November and December are historically the wettest months of the year, you'll probably be seeing a lot more damp residents traipsing around town as they try to complete their holiday errands. This brings up the old argument of whether you stay dryer by walking or running in the rain? In an effort to keep our holiday shoppers as dry as possible, I've done a little research on the subject that I think you'll find interesting.
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The first tendrils of fog came slithering through Deception pass like a giant octopus searching the seabed. The fog crept along the northern edge of Whidbey Island, flowed over the water until it reached Skagit Island, then retreated back to the pass. Eventually it dissipated altogether leaving behind a brilliant sunny day.

As I sat watching the fogs advances and retreats, I knew that while I was basking in bright sunshine residents on the west side of the island were shivering in the fog. That got me thinking about the various micro climates we have here on Fidalgo Island.
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