Friday, October 19, 2012

Sequim: Is It Really That Sunny?

Friday, October 19, 2012
11:03 A.M.

Happy Friday everyone!!!

Everybody talks about the Sequim rain shadow is the driest place in Western Washington, and for good reason. It is. They only get around 16 inches of rain each year, as they are northeast of the Olympics, and since the winter flow is generally from the southwest, especially during heavy rain events, the air descends off the Olympics, warms, and dries when it gets to Sequim. There is actually a type of native cactus that grows in Sequim. And even more impressive, they have a law that outlaws bad weather. I believe it was passed in 1995. Check this out!

"Sequim Municipal Ordinance 95-009, Section 2.1, "prohibits weather conditions that are detrimental to the enjoyment of activities within the city."

Mayor Bill Thomas sent a draft letter to Seattle TV weather forecasters saying "While watching your weather report . . . I noticed you placed your stinking little clouds . . . directly over Sequim while you were discussing Seattle weather. These folks are hardcore. Thomas also said "we'll be closely watching foreigners from Port Angeles and Port Townsend." The penalty for weather conditions that are detrimental to the enjoyment of activities within the city? Somebody proposed the idea of Bermuda shorts in the article I read, which can be found here. In the words of Thomas, "Hey, we're famous for our sunny weather, and we want to keep it that way." 

Sequim likes to brag about their rain shadow, but how much bragging rights do they really have? Let's take a look at the visible satellite picture over Washington right now.

12:00 pm PDT Fri 19 Oct 2012 - GOES West 1km Washington visible satellite

Sequim? Completely overcast. Why? Well, the flow over our area is from the west, not the southwest. When the flow is from the west, the Olympics do not block the flow over Sequim, and they get the same cloudy weather like the rest of Western Washington. Right now, the "rain shadow" is over Seattle due to the westerly flow, but alas, there is no cloud shadow to be found west of the Cascades.

But check out Eastern Washington, particularly on the east slopes of the Cascades. It is very sunny there! Thick clouds and lots of precipitation at and west of the Cascade crest, but once you get to Cle Elum and points east, it is completely sunny, except for a few orographically enhanced clouds over the higher terrain over there. Once you go further east, you get cloudy again. 

The east slopes of the Cascades are the sunniest place in Washington. My family owns some property in the Teanaway Valley, and a couple years back, some NYC businessman had a plan to build the world's largest solar power plant there, which would generate 75 megawatts of electricity. I'm usually all for clean energy, but I was actually against this solar plant simply because it would substantially lower the value of our property there. A lot of the other partners we shared the land with protested on the premise that the Teanaway Valley is NOT the sunniest place in Washington. After all, it gets over twice the amount of rain as nearby Ellensburg. So a lot of the partners turned to me to make a report showing how there are way sunnier places in Washington than the Teanaway Valley.

Unfortunately, I had to give them the cold hard facts. The Teanaway Valley is the best place in Washington to build a huge solar reserve. It is close to I-90, so energy can be distributed easily, and it is the sunniest place in Washington. Eastern Washington can be thought of as a "bowl," since it is surrounded by the Cascades, the Okanogan Highlands to the north, the Rockies to the far east, and the Blue Mountains to the southeast. In the Columbia Basin, cold air collects at the surface and creates an inversion, with low stratus clouds and fog often shrouding the basin in the winter. The east slopes of the Cascades are high enough that they are out of this inversion, but they still receive the drying effects of being on the lee side of the Cascades. In fact, even when there is no inversion, they are often still sunnier than Eastern Washington because the air sinks at a faster rate on the east slopes of the Cascades, so it is harder for clouds to form. Just take a look at the satellite picture above!

And yes, it is easier for moisture to make it over to Cle Elum than it is to Ellensburg, but rainfall doesn't necessarily translate into sunshine.

I was also looking at the radar images, and I found some pretty cool ones. They really show how strong the orographic lifting is right now over the Cascades and how much precipitation is falling on the windward sides of them. Check this picture out.

14:23 pm PDT Fri 19 Oct 2012 - UW composite radar image

Wow! Tons of precip over the Cascades, and zip once you get a couple miles east of the crest. Also, there's a pretty hefty convergence zone to our north. Convergence zones are really cool, and often occur simultaneously with the heavy orographically-enhanced precipitation over the Cascades, because they both occur in a post frontal, westerly flow off the Pacific.

Ok, one more thing. I took a look at the 12z WRF-GFS model this morning, and was astounded by the amount of snowfall forecast over the Cascades. Check this out.

Valid 05:00 pm PDT Sat, 20 Oct 2012 - 36hr Fcst - UW 12km 12z WRF-GFS 24-hour snowfall

Previous forecasts by the NWS had 3-8 inches of snow in the Cascades with a snow level at 3000 feet. Judging by this model, the Cascades above 2000 feet could see 18-30 inches of snow. That is a huge jump, and I'm not quite sure what to make of it, but I think we will see substantially more snow than previously forecast. I'm taking the middle road, forecasting 1-2 feet above 2,500 feet. 

One thing's for sure. If we get a ton of snow, I'm changing my Facebook profile picture to a cam of the snow at Snoqualmie Pass. It's been far too long since I've seen snow on that road.

Have a good one!

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