Wednesday, January 7, 2009

Just a little change in angle makes all the difference

A look at the current radar shows a major change from this morning...the rain shadow protection of Seattle is gone and now the rain shadow is NE of the Olympics. Moderate to heavy rain is now spread over the entire region from the Olympics to the Cascades. Why the change? The flow direction on the coast has shifted slightly from nearly westerly to southwesterly. You can see this by looking at the observations in the vertical (called a "sounding") at Quillayute on the coast (see figures). These observations are taken by balloon-launched weather observations (radiosondes) twice a day (4 am and 4 PM).

The first sounding is for 4 AM and you can see the winds (blue pennants) are nearly westerly at low levels...the second one is 4 PM this afternoon....a turn to the SW. The Y axis is pressure...850 (millibars) is about 5000 ft and 700 is about 10000 ft. The red line is temp and the blue dashed is dew point. The x axis of the plot is temperature in C.

The storm total precipitation from the local radar is shown below...pretty amazing..with some values over 15 inches! Note..this is uncalibrated and the radar could be high...but this is a major event and some rivers are hitting record amounts.

Interestingly the computer simulations were indicating record streamflows yesterday...these are from combining atmospheric and hydrological models...that is why the National Weather Service was hitting it so hard. I could hardly believe what they were I do.


Anonymous said...

How many inches would we have if this were snow rather than rain? Would we be Spokane?

Anonymous said...


Why is the weather in the puget trough seemingly getting more and more extreme in the temperature oscillation over the past decade?

Having lived here for 40 years, it seems that the two fronts that move in from the arctic and tropic direction happen with more energy and less predictability than they have in the past decades.

Do you have an explanation for the layman?

Anonymous said...

Cliff, The rain gauge data at ATG roof UW is showing nearly 8-inches of rain over the last 8 hours. This has got to be wrong, no?

JewelyaZ said...

My new rain gauge is showing seven inches of rain since I put it up at 1 pm yesterday (in East Bellevue). I'm guessing that that 8" measurement could be accurate. It's like a monsoon around here!!

Jeff said...

Here on top of the north end of the Sammamish Plateau I only recorded a dismal 1.18" through midnight.

Most the day near downtown Bellevue where I work was just a breezy drizzle until mid afternoon when the winds shifted and the rain picked up.

When I got home to Sammamish about 4 it had started to rain hard and did so until around midnight.

It was amazing to watch the NWS radar during the day and see how much rain everyone outside the rain shadow was getting.

December 07 I recorded 2.99" and was really hoping to top that but didn't even come close.


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Anonymous said...

I'm waiting for the Snoqualmie Casino to start advertising boat rides...(anyone else completely sick of their advertising?)

cornbread said...

^^^^ YES

6 7/8" rain in Maple Valley.

Jessica said...

Oh my YES, sick of the advertising! And I wonder if the lights from the casino radiate down to poor Snoq. at night.

I am so glad you provided the radar pics & info for the rainshadow Cliff. Yesterday, before all the emergency responses started occurring at flooded areas, I kept thinking our rain was very moderate in Seattle. Where was the "river in the sky" I wondered.

Our friends who live below Snoq Falls say that that this was well beyond '06 levels yesterday afternoon -- before it peaked.

Anonymous said...

Snoqualmie Falls would certainly be amazing -- that is if you could get there....

camco said...

Is infrastructure/stimulus money better spent on more snow removal equipment? Ha!

We need desperately to do whatever is necessary to remove as much of the ravages of development and "rebuild" the natural wetland infrastructure before we all get washed away.
The inconvenience of some snow every ten years or so is nothing compared to the mounting flooding problems.


Cliff Mass Weather Blog said...

The rain gauge from the department is in error...the real amount is about 1.4 inches...

Julia said...

Camco has an important point about the most important infrastructure needs around Puget Sound; worst thing is, there are a lot of developments built prior to 1979 which are sitting on what were, until then, winter wetlands, and which may need to be purchased and razed to restore anything like full stormwater capacity. Stormwater reinfiltration plants which depend on pumping instead of gravity (like the Lacey/Lott project on Martin Way) help, but they are also prone to failure at the most destructive possible moment; working with the natural topography is cheaper and less prone to fail in disaster.

Request for Cliff Could you discuss wind gaps in the Willapa/Black Hills/Olympic massif and how they effect storm impact in the Puget Sound region. Also, what exactly is the dynamic that leaves Kalaloch and Ozette dry when everything inland is getting heavy rain?

climo man said...

Well, winter was interesting, at least for a while,this year. It looks like the boring west coast high pressure ridge will be back for the next week or two.There won`t be much to talk about other than whether an offshore flow and warm temps (the sun!) or air stagnation and cool foggy conditions develop next week.During this period,the maximum temp records at Sea-Tac are relatively weak--mid to upper 50`s--so some records could be broken if the high builds inland with enough amplitude, as the progs are currently showing.

Anonymous said...

5:30 PM Thursday-Reports of very strong winds and temperature falling to 37 degrees in West Olympia....nothing on the news. Any information much appreciated. Thank you.