High Winds Hit the Eastern Cascade Slopes

The big weather action today was on the eastern slopes of the Cascades, where winds were gusting nearly to 100 mph at some locations-- 96 mph at Mission Ridge.  Here are the winds at 7 pm and 7 AM, with the red numbers giving you the gusts:

7 AM

7 PM

The winds were very variable and intermittent...some places got hit by strong gusts for a while and later experienced light winds.  Here are the winds today at a high (6730 ft) east-slope location--Mission Ridge:

Some mighty good windchill up there! In contrast, winds at Ellensburg were only gusting into the 30s (knots)

Now to understand these winds one must begin by noting we have had a VERY powerful jetstream over the Pacific that has headed right into us from the northwest.
Here is the upper level chart at 300 hPa (around 31,000 ft) at 4 PM Sunday..   Some winds are well over 150 knots, with some reaching 190 kt (219 mph!!).  Don't try to fly to Asia...it will take forever.

Winds indicate by dashed lines and barbs.

These strong winds have interacted with the Cascades.  First, air approaching the mountains rise, cool, becomes more dense and causes a windward high pressure area.  As air descends, it warms, becomes less dense and produces a lee trough.   Air accelerates as it goes from high to low pressure.  And such a pressure distribution was evident across the Cascades today (see map below at 10 AM).  Here is the proof.

And the interaction of the strong flow with the mountains can produce mountain waves that can bring down the momentum from aloft and enhance wind speed.   Here is an east-west vertical cross section across the Cascade today and you can see this effect (shading indicates wind speeds--dark red is strong, and air flow tends to follow the solid lines):

Lets take a look at the wind gust prediction at the surface (really 10 meters) from the high resolution WRF model today at 4 PM.  The first is from the 4-km grid spacing domain and the second is from our ultra-resolution 4/3 km domain.  Lots of gusts over 50 kts in the high-resolution domain.

 Hate to say it...but there will be plenty more of this over the next few days.

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The Weather Takes Its Gloves Off--Strong Winds and Mountain Snow

Missing Dog Update:  My dog Leah was seen near the Moose Casino in Mountlake Terrace--66th Ave W and 220th St SW.  If anyone is in the area and sees here, let us know right away! (see link on right)

We are now going into a very different, and much more active, weather period--and it starts today!

A strong front is now approaching the Washington coast and it will result in VERY strong winds in the Strait of Juan de Fuca, possible damage (power outages, localized flooding on Whidbey Island), blustery conditions and rain elsewhere, and snow in the mountains.  And I don't even want to tell you what the models are suggesting for next weekend. 

Perhaps the most profound weather phenomenon today is one I am actively researching:  a powerful westerly wind surge in the Strait of Juan de Fuca.

 Under the proper conditions, strong westerly winds can surge eastward into the Strait, reaching speeds of 50- 80 mph.  Sometimes called Westerly Strait Surges,  one will occur today.   A particular strong surge destroyed Ivar's Mukilteo Landing restaurant in 2003 (now rebuilt and my favorite restaurant) and another heavily damaged the Washington Ferry Elwha when it was under repair in Everett Harbor (December 1990).  Some pics of the damaged and rebuilt Ivars, which now has a weather theme:

The situation associated with westerly straight surges will occur today:  a broad ridge over the eastern Pacific, northwesterly uper-level flow over western Washington, and a sharp trough pushing into our region in this flow.   Here is the situation predicted for this afternoon at 500 hPa--about 18,000 ft above the surface:

You can see the strong trough embedded in intense northwesterly flow (remember the flow is parallel to the height lines and close spacing means strong winds).  As the trough passes through the winds aloft are aligned with the Strait....here are the height lines at 850 hPa (around 5000 ft) to illustrate:

You see how the height lines, and thus winds, are parallel to the Strait?  And the strong gradient of the height lines (thus strong winds) are clear.  At the surface, the front is associated with a trough of low pressure, so as it passes eastward an intense low level pressure difference (high to the west, low to the east) develops and air likes to accelerate from high to low pressure. Here is the sea level pressure forecast for this afternoon at 4 PM. Pressure is increasing rapidly up the Strait.

Strong northwesterly winds aloft and big pressure difference down the Strait both support strong westerly winds that can slam in the eastern Strait, with Whidbey Island, Everett, and vicinity taking the brunt of it.  Winds can gust to 40-80 mph.   This one is not completely ideal....so I would not look beyond 60 mph today.  Here are the WRF model forecasts for this afternoon at 1 PM.  Strong sustained winds of 35 knots have pushed into the Strait (and gusts would be stronger).

Three hours later, strong winds have reached Whidbey Island and the eastern Strait (Port Townsend and the NE tip of the Olympic Peninsula should get a taste of this as well).

The freezing and snow levels should drop as cold air behind the front floods the region.  With the flow directed up the mountains, enhanced precipitation in the form of snow should hit the mountains at and above pass level (more at the higher passes of course).  Here is the forecast 24-h snowfall  ending 4 AM on Saturday.  The model suggests a foot in the northern Cascades dropping to an inch perhaps at Snoqualmie.

Then another system comes in on Saturday with more rain in the lowlands and snow in the Cascades.  Here is the snowfall for the next 24-h--even more!

Good news for skiers!...we are going to start building the base they long for.  Skiing by Thanksgiving may well be in sight.

And now let me tell you something that I shouldn't.   The last few model cycles are suggesting a turn to colder temperatures on Thursday and the potential for lowland snow late Thursday or Friday.  Too early to be sure at this point...so don't get too excited yet.  I went to a meeting run by Seattle DOT this week on winter weather response...these folks are really girding up for battle.  And this year they will have the new UW snow-weather application: SNOWWATCH...which I will describe this week.

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Bering Superstorm

An extraordinarily intense storm is now churning through the Bering Sea.

The central pressure is roughly 945 hPa--similar to a category three hurricane, and in fact this storm does have hurricane-force winds.  (a hPa is the same as a millibar, mb, which you may be more familiar with.  In the inches of mercury units this would be 27.9 inches).  Take a look at a recent National Weather Surface surface analysis (for 4 PM Tuesday).  943 hPa low center and the NWS folks note the hurricane-force winds (sustained winds of 64 kt or more).  That is a lot of isobars, with extraordinary pressure gradients.

It is quite unusual to have a storm this strong so far north.   This storm developed very rapidly--approximately 60 hPa in 48 h, thus putting it in the category of explosive deepeners or "meteorological bombs" as known in the weather literature. Here is an image of the storm from of the polar orbiter weather satellites...the low center is in the middle of the swirl.

This storm is far deeper and stronger than the famous "Perfect Storm" of movie fame--at its most intense that low only got down to 972 hPa...nearly 30 hPa higher pressure.  The has passed near a few weather buoys.  Here are a few samples. Buoy 46070, found in the western Bering (see map) had a minimum pressure  of 28.2 inches of Hg (954 hPa) and gust to nearly 60 kts.

 Or Buoy 46035 (to the east) with gusts to 75 knots!

Wave heights at these locations climbed above 35 ft:

The fact that the storm is moving so quickly is preventing the waves from getting catastrophic since big waves requires strong winds, large fetch, and duration to build. Coastal flooding (up to 10 feet storm surge) and blizzard conditions add to the mix.  In any case, this will be one of the great storms of the year.

Selected Peak Gusts from the NWS Hydrometeorological Prediction Center

.SELECTED PEAK WIND GUSTS IN MILES PER HOUR 

...ALASKA...
TIN CITY AFS (AWOS)                   85                     
WALES                                 84                     
CAPE LISBURNE(AWOS)                   75                     
KOTZEBUE/RALPH WIEN (ASOS)            73                     
KIVALINA ARPT                         71                     
POINT HOPE (AWOS)                     69                     
CAPE ROMANZOFF (AWOS)                 60                     
ST MICHAEL                            58                     
TELLER                                58                     
EMMONAK                               56                     
NOME (ASOS)                           55                     
BETHEL AIRPORT (ASOS)                 54                     
SAVOONGA AIRPORT                      54                     

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Boring with a Hint of La Nina

Sometimes the early part of  November is the quiet before the storm;  this has been true for the last few days and will continue for the remainder of the week.  But don't forget:  the last week of November on average brings the stormiest, wettest, meanest weather to the region.  Meteorological ground zero for the Northwest.  Turkey on the barbecue.  And sometimes lowland snow--like November 22nd of last year.

Just to show you what I mean by boring, here is the National Weather Service forecast for this week:

Some clouds, some sun, a few light showers, temps reaching the 50s and dropping into the mid to lower 40s.  Enough to drive a meteorologist mad.

But there are some interesting aspects of the atmospheric situation of the next few days, some indicative of our old friend-La Nina.  Take a look at the 500 hPa upper level chart for Tuesday at 1 PM. A ridge over us (thus dry) and a high amplitude trough digging south from Alaska.

No umbrellas needed here.   During the next few days an amazing thing happens.  The trough deepens into a closed low off of California and becomes isolated from the jet stream to the north over the north Pacific and southern Canada. (remember the air flows parallel to the lines and is stronger where the lines are closer together).

There is a fancy name for this situation--a cut-off low:  the low is cut-off from the jet stream.   We are left in the dead zone...not much flow, not much action.  And you will notice a BIG ridge (High) over the central Pacific--we will get back to that. Here is the precipitation over the West Coast for the next 72h.  The action is pretty much all offshore.

But then things change a bit for Friday.   The ridge builds offshore  and the Northwest is in northwesterly flow (see below).  A weak trough is embedded in this flow..which should bring some clouds and perhaps some light rain. Not too scary, but this pattern is reminiscent of a La Nina configuration, like last year when we were stuck in cold, northwesterly flow for months.  If a trough develops with more amplitude and the ridge extends more into AK, we approach the canonical snow pattern.

On on Saturday...more of the same, but a bit stronger (see below).  Expect a low snow level and decent snows in the mountain.  The Mayor and SDOT don't have to worry...yet.

Don't forget to vote tomorrow...

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The Great Raindrop Deception

You have been deceived...by magazines, newspapers, the digital media, by artists, school teachers, and yes, even children's books.  And it will stop here.

When raindrops are drawn, they almost always look the same way, as a teardrop.  Some samples:

The problems is that raindrops virtually NEVER look like this!  Northwesterns like us, with our persistent wet weather, should be expected to be fully educated in raindrop-ology, and thus this blog may serve as an important public service.  Perhaps the Mayor will establish a raindrop education day this year.

Well, if raindrops never look like teardrops, what DO they look like?  Well, it turns out that their shape depends on their size, a situation also obvious in humans.  Small droplets are spherical, bigger ones like pancakes, and very large ones like parachutes.   His is a graphical rendition:

Drizzle droplets (a Northwest favorite), with sizes of roughly  .3 to .5 millimeter (mm), up to small raindrops, of approximately 1-1.5 mm, look pretty spherical. (For the metrically challenged... 1 mm is about .04 inches)

Why spherical?  Surface tension--the attraction of water molecules to each other--pull the molecules together into a ball.  Furthermore, small droplets don't weight that much and their fall velocity (also known as the terminal velocity) is relatively small, so the disturbing influence of the air moving around the droplets is minimal.  I bet you have all noticed the difference in fall velocity of various size raindrops:  drizzle drops seem to slowly drift down while big rains come down REAL fast.

For bigger droplets (2-3 mm), their weight causes them to fall faster, and the greater speed of the air passing around them causes them to be distorted into a pancake shape, with a nice little dimple in the middle.

For really big droplets, the distortion caused by the fast moving air is huge...the droplets get hollowed out into a parachute-like shape.

There is a limit to how big a raindrop can get because eventually the aerodynamics forces of the passing air tears it apart.   What is the biggest raindrop ever observed?   Well my University of Washington colleagues (Dr. Peter Hobbs and Art Rangno) may have seen the largest---8.8 mm (.35 inches!!)--in tropical cumulus.   Imagine being hit by such a giant raindrops!

One final thing--our newly upgraded weather radars, with their fancy dual-polarization, have the capability to measure the shape of precipitation, including raindrops. Here is an example--the zdr product (stands for differential reflectivity).   Zdr measures the difference in return between an up-down and side to side view of precipitation, thus giving information on the shape.  When the returns in both directions are roughly the same (the difference between them being nearly zero), this product gives a value near zero. If the precipitation gets distorted, the number increases.  Pretty neat stuff--measuring raindrop shape remotely.  Looking at the image below, you can see a lot of near zero (blue) colors....not many teardrops here! The area of large values (white/gray colors) near Hoquiam is not meteorological--its ground clutter, where the radar beam is hitting the surface.

Zdr from the new NWS Langley Hill Doppler Radar

Finally, for those voters in Seattle, please keep in mind the Seattle School Board race and necessity to replace the current board members with those committed to better math education in our schools.  The math textbooks used in Seattle are terrible at all levels and I see the impact on Seattle students coming to the UW--many of them have very weak math skills.  We can do much better, this requires school board members that are willing to deal with the issue--the incumbents are not.  The challengers (Peaslee, McLaren, Martin, Buetow) are all committed to dealing with the problem. The latest school board poll is here.

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Mamma Mia! That's a Nice Front!

Some nights are better than other for weather lovers, and tonight was a good one, with the strongest front of the fall moving through the region.

The new Langley Hill radar made it very clear that the approaching front was worth of some respect, with an extensive area of moderate and heavy rain. In the old days, we really would not have known this.

And we could savor the front as it made landfall and moved across the western lowlands.

Precipitation totals over the central and southern Sound were quite respectable, as shown the Seattle Rainwatch: .25-1 inch in many locations. Mayor McGinn introduced Rainwatch this week and it sent out warnings before the event.

Seattle Rainwatch 24-h totals ending around 9 PM Wed.

And the winds.... on the coast and over the eastern Strait, the winds gusted to 40-55 mph, while here in the lowlands, winds hit 30-35 mph, particularly over the water.   Here is a plot of the wind gusts at Destruction Is, off the central WA coast---gust to 49 knots....56 mph.  More than many folks saw for "Hurricane" Irene in NY and New England..

The strong, turbulent winds picked up the prodigiously falling leaves to create quite a spectacular scene in my neighborhood.  Driving rain, gusting, roaring winds, a torrent of leaves--folks, it doesn't get better than this.   And to frost the cake, during the next few hours light snow will fall in the mountains above roughly 3000 ft.

Northwest storm season has begun.

Finally, here is a marvelous video of today's show, starting with dense fog this morning that surges in and out, then clearing skies, followed by lowering cloud decks from the approaching front, and then heavy rain. Watch the speed of the clouds...the atmosphere goes into warp drive later in the day:

http://www.atmos.washington.edu/images/webcam0/movies/20111102.mov


If you are a Seattle resident and would like to participate in a poll on the Seattle School Board race, click here: http://www.easypolls.net/poll.html?p=4eb22007011eb0e4496235ab

Thursday Update: Snow in the Passes

No skiing....yet.

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The Return of Mountain Snow and Some KUOW Comments

October is now over and it was a very benign month, with temperatures and precipitation very close to normal.   No big storms.  A few weak fronts.  Occasional sunny days and plenty of fog.  And very little snow in the mountains.

But it looks like this is going to change, with the mountains beginning to build the wintertime base of snow that all skiers long for.

The first shot comes on Thursday, when a very deep trough moves over the West Coast, pushing the jet stream into California.  Take a look at this 500 mb upper level chart at 2 PM on Thursday (below)...quite a deep trough over the northwest...and lots of rain and weather going into southern CA and the Southwest.  Bad time in lotus land! And a huge ridge in the eastern Pacific....reminiscent of a La Nina-type pattern.

Here is the snowfall for the 24-h period ending 5 PM on Thursday--several inches in the Cascades--with some of it getting down to pass level (snow level descends to roughly 2500 ft).  Not much, but a start.

Then another trough moves in on Saturday, and again the bulk of the flow going into California.

This relatively weak feature only provides a dusting of snow over the Cascades, perhaps and inch or two at the most. 

But then on Monday another trough approaches--stronger and embedded in much stronger flow.  This system could produce FAR heavier snowfall, with totals reaching a foot or more.

Of course, our confidence in the forecast declines in time, but it is clear that during the next week, a colder, wetter pattern more reminiscent of the La Nina situation of last year will set up.  In fact, the NWS Climate Prediction Center forecasts for the next 6-10 days is for colder than normal and wetter than normal conditions (see graphics)---enough to warm the hearts of Northwest skiers hoping for an early start to the season.  And yes...a reminder of last year.

KUOW Update

I have been fairly quiet about KUOW recently, not the least because I am really enjoying doing my weekly weather program on KPLU (Fridays at 9 AM) with Keith Seinfeld, their excellent science reporter.  But all too often I get reminded about the attitudes over at KUOW, and particularly at Weekday, that I found so disturbing when I was on the inside.  Case in point:  Joel Connelly, the well-known PI reporter.   This week Joel wrote the following:

"Not long ago, on KUOW Radio -- before being exiled for protesting their ouster of weather expert Cliff Mass..."

Joel was one of the wisest and principled voices on the 10 AM "Week in Review" Friday program on KUOW, and a wonderful counterweight to the very conservative views of the Seattle Times' Joni Balter.   He was a vocal critic of my "firing" for the terrible sin of talking about an education issue on one program--and wrote a very supportive piece in the PI on the subject.  Turns out that criticism of Weekday staff  or KUOW management is not allowed by this public radio station.  It appears that by speaking his mind, Joel was given the boot....in a very similar way I was given the boot when I disagreed privately with Steve Scher's approach of selectively allowing certain opinions on his show.  Folks--this is very disappointing behavior and quite frankly unacceptable for those responsible for a very important public radio outlet--a station whose license is held by the University of Washington.

And as long as I am complaining, why does KUOW Weekday insist on using a non-meteorologist, posing as a meteorologist, on many of their Friday shows?   This is about as reasonable as having a person without a medical degree doing surgery or providing detailed medical advice.  And what does this say about journalistic integrity?  The KUOW audience deserves better. 

Local American Meteorological Society Meeting on Friday:  Open to All

The Puget Sound Chapter of the American Meteorological Society will be meeting on Wednesday, November 2 at the Northeast Branch of the Seattle Public Library at 6:30 PM.   UW Graduate Student Luke Madaus will describe the new dual-polarization products available from the newly upgraded National Weather Service radars.  All welcome.   Location: 6801 35th Ave. N.E.  More directions at: http://www.spl.org/locations/northeast-branch/net-getting-to-the-branch

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