Wednesday, December 17, 2014

A Review Of The Windstorm

Wednesday, December 17, 2014
1:46 pm

Last Thursday night, right after I had finished my final, my mom and I decided to trek up to Sandy Hook, which is a little coastal community situated on Cultus Bay on the southern tip of Whidbey Island, to catch what ended up being the biggest windstorm of the year thus far for the Pacific Northwest as a whole, and some of the strongest winds I have experienced in my entire life. Here, I'll just give a general overview of the storm, and I'll show you some pictures and videos that I took up at Sandy Hook Thursday night and Friday morning.

First off, let's take a look at an animation of the windstorm. The loop below shows water vapor satellite imagery from November 29th to December 14th. Our windstorm begins forming to our southwest at about 0:21 and passes over our area at around 0:24.

Here's a more in-depth picture when it was near peak strength. Look at the beautiful, symmetrical form of the cyclone, and how tightly the bent-back-occlusion wraps around the center of circulation. It almost looks like a hurricane. Pretty extraordinary.

8 pm December 10, 2014 (PST). Retrieved from NOAA WRH Satellite Loop.

As I explained in my previous post, this cyclone was a "Sou'wester." Most of our major regionwide windstorms have been of the "Sou'wester" type. The Hanukkah Eve Storm was the most destructive storm for Puget Sound since the great Columbus Day Storm of 1962, but it was not a truly region-wide storm. This storm affected everywhere from San Francisco (they actually closed schools due to the wind and rain from this storm... wimps) to Vancouver Island and Southern British Columbia. Seattle did not experience anywhere near the amount of damage it experienced with the Hanukkah Eve Storm, but if this storm had kept its strength as it tracked northward and if it had tracked a bit further east through the Chehalis Gap, the winds could have approached Hanukkah Eve levels.

One of the most striking things about this storm is how closely its track mirrored that of the Columbus Day Storm. Take a look at this picture below comparing it to other famous Sou'westers to strike the Pacific Northwest. You can see that its central pressure is much higher, hence the lower winds over much of the area. However, it tracked much more closely to the coast, and if it had deepened to 960 millibars or lower, there is a distinct possibility that it could have caused the tremendous winds witnessed in 1962.

Credit: NOAA

I wasn't able to find a definitive list of the highest gusts throughout the entire Pacific Northwest region, but I was able to find some gust information for some individual areas. I put a small list together of gusts that I thought that were particularly notable. Values given are in mph. I have a more complete list of gusts below from the Seattle, Portland, and Pendleton NWS forecast offices. I looked but I could not find any reports from California NWS offices

NWS Portland gusts
NWS Seattle gusts
NWS Pendleton gusts


White Mountain: 139
Mount Lincoln: 135
Slide Mountain: 112
Mammoth Summit (yes, the ski area): 111
Alpine Meadows: 109

San Francisco: 50
Oakland: 46


Mt. Hebo (3160 ft): 90
Sea Lion Caves: 89
Marys Peak (4137 ft): 88
Newport (120 ft): 72
Portland (30 ft): 67
Garibaldi: 64
Salem: 53


Crystal Mountain (6870): 97
Mission Ridge: 78
Mt. Baker (5000 ft): 78
Naselle Ridge (2008 ft): 77
Port Townsend (28 ft): 70
Whidbey Island Naval Air Station (47 ft): 69
Hood Canal Bridge : 63
Cape Disappointment: 63
Paine Field (Everett): 62
Useless Bay: 59 (this is the closest location to where I was)
Hoquiam (12 ft): 56
520 Floating Bridge: 51
Boeing Field: 49
Sea-Tac (370 ft): 49
Tacoma Narrows Airport: 48

As you can see, the highest winds generally occurred on mountain ridgetops. I heard rumors of Mt. Hebo having a 130 mph gust, but this figure did not show up in the official NWS list. Portland's gust of 67 mph was actually the strongest gust since the great Sou'wester of December 12, 1995, so this storm was no slouch.

Also, just for funsies, let's take a look at all the rain that fell in California. While Seattle and Oregon weren't extraordinarily wet, California, particularly San Francisco and areas north, got absolutely soaked. This storm was fantastic for drought relief, but it would take 4-5 more of these to end what is the worst drought for California in at least 1,200 years.

Going back to our region, some of the highest winds in all of Western Washington were located right where I was. Useless Bay is that larger Bay that is to the west of Scatchet Head on the southern tip of Whidbey Island. This lines up well with what the UW's WRF-GFS model was predicting at the time; note how the highest winds are there and regions to the south over the water.

Valid 10:00 pm PST, Thu 11 Dec 2014 - 18hr Fcst

Anyway, let's take a somber look at some of the catastrophic damage inflicted upon the residents of Sandy Hook.

Play structures were ripped to shreds...

Furniture across our backyard was slaughtered...

And I would have loved to witness the gust that put this chair in this precarious position.

But all dishevelment of lawn furniture and children's play structures aside, there was some moderate property damage as well. Our "crab shack" got slightly de-roofed, which may end up being a blessing in disguise, as we now have an excuse to give it a new one. I didn't take a picture of it, but our 18-20 foot aluminum canoe got blown right off our dock and drifted a good quarter-of-a-mile down the man-made canal that our dock lies on. We are very lucky to have found it!

A big wooden fence that surrounded the community swimming pool toppled over under the storm's strong gusts.

Also, some similar fences right off the bay slightly leaned over due to the strong winds coming off the Sound. All in all, the structural damage doesn't look like much, but after witnessing how strong the winds were and how they hardly caused any damage, I've really gained an appreciation for the extreme strength of winds when significant structural damage is evident.

When we drove out to go back to Seattle, there were tons of branches all over the road and many downed trees that had taken out power lines. Our power was out for two days.

Lastly, here's something that's unrelated to the winds but is related to the low pressure system itself. With such low pressure over us in tandem with astronomically high tides, the observed tide was as high as I had ever seen it and almost passed over our dock. Pretty incredible.

On a final note, I'll leave you with some videos that I took. Here's one that shows how noisy our house was on that night, with some tasteful lighting to boot.

And here's the piece de resistance... an on-site video of the storm itself. I was recording right above a breakwall on the coast that was actually very close to the children's play structure that got thrown around. I'd estimate that winds were a good 50-55 on the water at that time, but as they went over the breakwall they accelerated as the wind was noticeably stronger there than right on the water.

I'll have more blogs coming soon, including ones regarding the potential for cold in the extended future. However, the short term forecast holds flooding, primarily for Oregon, where over 15 inches of rain may fall in select locations over the weekend.


Wednesday, December 10, 2014

Major Windstorm Tomorrow?

Wednesday, December 10, 2014
12:30 pm

I've got one more final tomorrow at 11:30 am, but here I am, blogging away my anxiety. Why on Earth would I put 40% of my grade on the line to write a stupid weather blog (and yes, I'm going to need all the time I have to study for this test. Kids, beware of atmospheric motions 441.)?

Because we might see a major windstorm tomorrow. 

Now, this isn't going to be a catastrophic windstorm for the Puget Sound lowlands, at least not at this point. Believe it or not, there were a couple models that were advertising that it could be. I define a "catastrophic windstorm" to be a storm with widespread gusts to 60-70 mph in our region. While that may not be a lot for the coast, it's a pretty big deal for the inland areas west of the Cascades. And with our saturated soils and excess of giant evergreens, you can bet that 60-70 mile per hour winds here are going to cause a lot more damage than equivalent winds in the Great Plains or even New York City. I would say our last catastrophic storm was the Hanukkah Eve Storm of 2006. This storm doesn't look to equal that one in magnitude for our region, but it could be one of the strongest since then. It could be. 

Why all the uncertainty? The storm is 24 hours out, so shouldn't we be smart enough to know if we're all going to die a grisly death? Well, the answer is yes, but the reality is no. The models have been inconsistent with the storm, but honestly, that's not the biggest problem. It's the very nature of the storm that were dealing with.

You know those Nor'easters they get on the East Coast? Well, this is its Northwestern cousin, the "Sou'wester." These are the storms that are historically the most damaging storms to our area, and they tend to impact the entire west coast. The last really big one was in December 1995, creating gusts of 72 mph from Cape Mendocino, CA to 76 mph up in Bellingham, WA. Portland hit 74, Sea-Tac hit 60, and Mukilteo, just to the north of Seattle, hit 86. And Cannon Beach, Newport, and Sea Lion Caves on the Oregon Coast all hit well above 100 mph.

The Columbus Day Storm of 1962 was also a Sou'wester, and any Pacific Northwest weather aficionado is familiar with "The Big Blow." With 179 mph winds at Cape Blanco, 116 mph winds in Portland, 127 in Corvallis, 100 in Redmond... you get the point. The Columbus Day Storm was the David Banner of Pacific Northwest windstorms, and we likely will not see one like it for hundreds of years. All these diagrams were taken from Wolf Read's The Storm King website.

I'd love to go on and on about massive Sou'westers, but you get the point. These are the big storms. They typically form south of Eureka around 135 West, and from there, they rapidly intensify and curl northward. Depending on how close they get to the coast, they can bring strong winds to an extremely large area. The Columbus Day Storm nearly paralleled the coast from California to Vancouver Island and remained just offshore, giving all areas a tremendous blow. Conversely, the Hanukka Eve storm came from the WSW and crossed Vancouver Island, only delivering its main blow to Washington as it never got close enough to the California and Oregon coasts for them to feel the full effect. Take a look at the pics below and notice the difference in tracks.

You can see how the Columbus Day Storm would have impacted a much wider area. Additionally, it was much deeper, so that contributed to the breadth and magnitude of destruction. AND, it occurred, on, well, Columbus Day, when many trees still had their leaves. Truly a worst-case scenario for destruction, yet a fascinating one from a meteorological point of view.

Now that you have a little background on Sou'westers, let's get back to talking about our forecast. As the track from the Columbus Day Storm shows, even a slight displacement to the west would have weakened the winds significantly across the region. Storms like the Hanukkah Eve Storm shown above that smash into southern Vancouver Island from the SW are not nearly as sensitive to changes in track. That's what makes this forecast so hard. Tiny changes in track with these types of storms mean major changes in effects. Remind you of another type of forecast here? (hint: it starts with an 's'). The National Weather Service sums this up well with their latest "weather story."

This specific storm has changed wobbled from making a direct pass right over Seattle to passing right off our coast, sparing us major winds. It will not even approach the Columbus Day Storm, and it will not be as strong as the Hanukkah Eve Storm even in a worst case scenario. The storm itself has a much higher pressure than the CDS; it bottoms out at around 970 off of the Californian Coast, and then it slowly weakens as it travels northward. Let's compare some previous model runs just so ya'll know what I'm talking about.

Here are the two most recent model runs from the UW. Last night's is below, and this morning's is below that.

Valid 01:00 pm PST, Thu 11 Dec 2014 - 45hr Fcst - Retrieved from UW mm5rt

Valid 01:00 pm PST, Thu 11 Dec 2014 - 33hr Fcst - Retrieved from UW mm5rt

You can see that the low this morning is further south (it is arriving later), weaker, and further offshore (this becomes even more apparent during later slides). However, I just checked the European model, and it is slightly closer with the low.

Credit: Weather Underground

Additionally, I just checked the latest 18z GFS, and it is ever so slightly closer with the low, although still offshore.

The bottom line:

I don't think this will be a major event for the Puget Sound lowlands. It will get windy, and there will be power outages. But I don't expect this to be a widespread, damaging event. The main reason is that regardless of the track, the low looks to be weakening too quickly as it heads up north.

However, as I said before, tiny changes will have big effects. We have a high wind watch over our area.

OK, NOW it's time to study. I might make a webcast tonight if I get some stuff done. Maybe.