Warning damaging windstorm…

Later today a strong windstorm will pummel western Washington and Oregon.

The cause: a mid latitude cyclone undergoing “explosive cyclogenesis” . I know, it sounds like a great name for a heavy metal band. “Live at the Emerald Casino: “Explosive Cyclogenesis”.

BUT: Take this storm seriously!

Get updates on Seattle National Weather Service website - there will be changes as the storm develops.

It is an incredible display, by Mother Nature, of rapid storm development. For short, we meteorologist call it a “bomb”. Technically, it’s deepening of one mb an hour, for 24 hrs. Damaging wind gusts will be 60-80mph, later today, mainly the coast, but 65mph in Puget Sound area, which is rare and extreme. This storm has its origins in Typhoon Songda, three days ago off Japan. It has come across the Pacific to give us a serious spanking. This is not uncommon, in the fall, to see this happen -- but the development and intensity, right in the sweet spot to cause us significant damage, is unusual. This is probably going to be a 1 in 10 year wind storm, and most intense wind storm landfall in a decade. However, this is not as strong as the famous NW Columbus Day storm of Oct 1962 – which is the greatest non-hurricane storm every to hit North America.

Many believe its origins, as a typhoon, is the energy source, but that is not the case. This storm has lost almost all of its previous spin and even much of its moisture. The central pressure, late yesterday, was a measly 1000 mb and producing, lame 10-15 mph winds. Something magical (explosive cyclogenesis) has happened this morning – it has lost its entire tropical legacy and is being re-born as a powerful extra tropical cyclone. Already it's producing > 57 mph winds, from ship reports. It's offshore to our SW with pressure at 983 mb pressure, measured at an off shore bouy and  rapidly falling.

A tropical storm’s energy is an engine, fueled by rapid condensation of warm water vapor, releasing heat. But a mid latitude storm is far grander – it’s engine is driven by the contrast of massive cool air from the north colliding with a huge body of warm moist air from the south. In today’s case, the process is being greatly optimized by a 160 kt jet stream aloft.

Again, take this storm seriously and be prepared.

Historical NW windstorms: http://www.climate.washington.edu/stormking

Change in seasonal forecast – for the better!

Thursday (Oct 13) there was a forecast update from the Climate Prediction Center. The forecast has been modified and is now predicting La Nina conditions this fall/winter. You might recall, they were saying cool Neutral, which is borderline La Nina. Well, we are now crossing threshold of critical ocean temperature cooling, in the tropical Pacific, to La Nina territory, likely for fall and possibly the winter. It doesn’t really change the forecast much, but gives the seasonal forecast more confidence, for snow. The outlook is for normal winter snowfall, perhaps leaning above normal snowfall, now with La Nina influence. Also, temperatures will not be as mild as the last couple of fall/winters. Fewer warm spells = more powder and lower snow levels. Plus, already we are getting an active early start with all the storminess.

Recent accumulating snow

We have had quite a bit of rain in the last couple of days: 2 - 11” .

The snow level has dropped a little, so we are seeing fresh snow on the upper slopes of some areas. You can see new snow above about 5,500 ft . My guess is a few inches to more than a foot in spots, so a great start for October. Snow levels will stay 5000-6000ft for the week ahead with some minor storms causing additional snowfall for the week ahead. Another 3 – 12 plus inches is possible, favoring Whistler and the North Cascades. Whistler Roundhouse below, Saturday am

 

Larry Schick

Meteorologist

Open Snow NW