Monday, November 22, 2010

Humility

One thing you learn in this business fast is humility.

Clearly, our model forecasts have had some problems and now the situation is now becoming clearer. Precipitation has spread was more intense and spread farther north than predicted. But the biggest threat was never this morning... all the models had only a few flurries over us. The 1-3 inch NWS forecast was for this afternoon and that is what we have to watch now. And a power glitch took out the UW modeling system last night..bad timing.

This is when forecasters make mistakes for psychological reasons...miss one way and overcompensate the other.

The key feature is a low center along the coast. Last night's model either had it too weak or mispositioned. Here is the latest surface observations at 10 AM. Click on the image to expand. A low center (roughly 1004 mb) is along the NW coast. If it moves SE we could get the set up for big lowland snow...moisture off the ocean circulates inland, being met by cold air coming down from the north. This cold air is driven by the difference in pressure between the cold, high over BC and the low pressure center.The NWS is clearly worried about this scenario and have put out a heavy snow warning for the lowlands. The latest high-resolution run--which has the coastal low better but not perfect-- shows the following:We are talking about 2-4 inches south of the city, with roughly 1-2 inches on the north side. More as you head towards the Cascades and south.

Can you believe this short-term forecast? The coastal low is clearly stronger and farther north than predicted by ANY of the models. I really wish we had the coastal radar now...it would provide a clear view of what we are dealing with...would have made a huge difference now.

The 11 AM surface map...just available shows a 1002 mb low over the NW tip of the Olympic Peninsula and the latest visible image show VERY unstable air offshore. If the low goes south of us and draws some of that cold, unstable air in...and it meets the cold stream from the north, we are talking about serious snow (6-12 inches). Or if the low moves farther north we could get a Puget Sound convergence zone over the central Sound and a huge amount of snow in a narrow band (a la Dec 18, 1990). The system is moving slower than the models predicted and the real threat is the middle and latter parts of this afternoon.


In short, a major threat is there, but there is a lot of uncertainty. You can watch the radar imagery to see this unfold...and know whether there is any threat. Here is the NWS radar link:

http://radar.weather.gov/radar.php?rid=atx&product=N0R&overlay=11101111&loop=no


Or you can view the evolving surface observations and track the low! One think is sure...it will get much colder tonight. It is critical for all local DOTs to get as much of this stuff off the road as possible or hit it with deicer. All untreated slush and water will freeze solid tonight.

36 comments:

cornbread said...

Steady snow in Maple Valley all morning. Close to 3" so far....

Cas said...
This comment has been removed by a blog administrator.
Dan McShane said...

Humility or a great learning experience? If we had this sort of weather patern all the time it would be a lot easier. That said thanks for the great updates and interpretations

superdeluxe said...

We have about 3 inches in Tukwila and still snowing hard..craziness.

Michael DeMarco said...

At 11:30 - three and a half hours of steady snow in Sequim, no wind yet. 5" accumulation now tops all of last year in one shot. We are just north of the town of Sequim at about 175'

sdpontiac said...

Where can one find a link or better yet, a time lapse loop of the cloud image from above?

Erika said...

Don't feel bad! Saturday a couple people mocked me for mentioning that I wanted to make a big run to the store in case it snowed.

I told them, "Cliff Mass is hedging his bets in a way that makes me a lot more nervous than any of the TV stations hollering about the end of the world."

And checkit - I was right! 1" of snow outside La Conner and it's still falling, and it sounds like we'll probably lose power this afternoon if those winds come through. But me? I am safe and sound with a pantry full of food. HAW HAW.

niko2k4 said...

Any early guesses about the moderation? Will areas such as Bellingham/up north go through an amount of snow before it turns back to rain, or should we be safe from that?

Scott K said...

Hey Cliff, thank you for the update. I'm sure we can all agree that weather forecasting is one of those 'damned if you do, damned if you don't' type of things.

I'm sure that we are all in agreement when I say we all appreciate your hard work and for keeping us blog readers up to date with your thoughts on the weather!

This afternoon sounds awesome, I'm really looking forward to more snow. The current radar (as of 12 noon) doesn't look too interesting, but hopefully in an hour or three things will change.

Cliff,
Are there going to be any changes for the traveling forecast? My wife and I are heading over to yakima either tomorrow or wednesday. I have an excellent snow car (subaru AWD + great snow tires, plus extra blankets, chains, etc in the car) so I'm not worried about the trip necessarily, but it would be nice to know what I should be expecting while going over the pass and into eastern washington along I-90.

Thank you!

Teresa said...

Have to wonder why the National Weather Service made much more accurate predictions, given that they don't have coastal radar either.

Maybe theoretical academic models should just be taken into account, not relied upon...just a suggestion. You in the ivory academic towers might want to have a long conversation with the pragmatists at the NWS about how they predict snow.

I've decided that all professional weather predictors should commit to driving an articulated metro bus on any day that they predict - "bottom line, no snow" -- when it's pretty obvious there's going to be snow. I'll bet their predictions would get a whole lot more pragmatic and cautious.

MyronsWorld said...

Cliff,

I am an amateur meteorologist (in other words, a fake one), but I have been a weather nut my entire life. The models almost never get these types of events correct. Too many variables. We saw this in 08-09. Let's not have short memories so we can nail this next time. With all the cold air rushing down, it was inevitable that the ensuing instability would wring out the slightest bit of moisture. We would also see significant embedded orographic events.

I am looking at model runs for Thurs/Fir, and I already think they are out to lunch. They are missing the depth and strength of the cold air mass. Any scouring out of the cold air will take a significant push of warm air. If the next system's push of warm air slows even a touch and the trajectory changes only slightly, we could see several inches before it changes to rain. It looks like most models are calling for temps in the 40s thurs/fri with rain. I believe some areas will be hard pressed to reach 40, and the cold air will be deep enough to support snow even with the overrunning warm air. Or worse, a freezing rain/sleet event for Seattle.

Erik

Michael said...

128' elevation Normandy park about 2 city blocks from the water we have : 2" of snow.
It was absolutely crazy out on 1st avenue and Des Moines Memorial drive. There were 5 cars in the ditch in a matter of 15 minutes.
Then the de-ice truck came and it was much better on the roads. People were abandoning cars and walking to wherever they lived, people sitting in the middle of the street putting on chains was a pretty bad idea if you ask me though...

roguedelux said...

It's ok Cliff, we love your fine details and analysis. Besides, isn't this why we *love* weather?

WanderChow said...

Uh-oh.

Raymond said...

You know, it is kind of fun watching you get this so wrong. I do not mean this as an attack. I am a BIG fan of this blog, and I just LOVE your book. But what I really like about this is just how difficult weather prediction really is. Despite all the new technologies and years of evaluations/monitoring, many times we are still at the mercy of Mother Nature. A sure thing is boring.... it is the exceptions that make it interesting.

I know you will get a bit of grief for your prior posts (and you probably do deserve some of it having just re-read some of them), but I am looking forward to your updates.

Thanks for the frequent updates, Cliff.

Raymond said...

You know, it is kind of fun watching you get this so wrong. I do not mean this as an attack. I am a BIG fan of this blog, and I just LOVE your book. But what I really like about this is just how difficult weather prediction really is. Despite all the new technologies and years of evaluations/monitoring, many times we are still at the mercy of Mother Nature. A sure thing is boring.... it is the exceptions that make it interesting.

I know you will get a bit of grief for your prior posts (and you probably do deserve some of it having just re-read some of them), but I am looking forward to your updates.

Thanks for the frequent updates, Cliff.

zach.burgess said...

Would having a coastal radar help predict the next 24 hours better?

Also been snowing pretty constantly in Woodinville and sticking to some pavement.

Vancruisers said...

Hi Cliff,

I love reading your weather blog even though I'm up North of you here in Vancouver - your insights regularly help provide great information!

Do you have access to the Canadian radar feeds? I'm guessing you get more than the "web" version for the ones in the states, but just in case you haven't seen them:

http://www.weatheroffice.gc.ca/radar/index_e.html?id=wuj

http://www.weatheroffice.gc.ca/radar/index_e.html?id=XSI

The XSI station is really badly placed unfortunately, and really misses some pretty important areas out to the West of Vancouver Island. Seems like a pretty major oversight!

Susan said...

12:53pm - About 3" depth so far on the west side of Gig Harbor, above Henderson Bay - measured on the top of my deck. It snowed fairly heavily and steadily all morning and right now has let up to just a few small flakes, but the sky has darkened within the past half hour.

Ferdi said...

I enjoy your blog Cliff. You are doing a nice job with it.

This is a pretty classic snow scenario for Western Washington where, as you say, cold air flowing out over the relatively warm Pacific enhances precipitation and not infrequently causes a deepening of a low pressure center or short wave traveling down the coast. I suspected that when the wind died down and it started to snow here in the islands.

mjgrota said...

Being a forecaster is like being a stock broker. You are rarely troubled by long periods of uninterrupted success.

Matt said...

Geez, right now the radar looks pretty clear, innocuous even. Yet reading the post I hear about low pressure pumping up moisture or even a 1990 convergence zone (I was stuck in that one). I'm at work right now and am wondering whether or not to take off early (I take the bus).

T said...

Where did all the snow go? Is the rain shadow in effect? I'm working just south of I-90 on Rainier Ave. We've had about half an inch so far today. Currently snowing very, very lightly. I can hardly see it coming down.

windlover said...

Almost 6 inches total here in Eatonville (about 5 7/8 to be exact!) And still coming down pretty good. Does it have to warm up later this week? Can't you be wrong about that too...please?

T said...

I need to 2nd what many other folks are saying. I love this blog! I Check it all the time, but especially during a weather event. Thanks Cliff!

Anne said...

Cliff,

Are you ignoring what's happening over here on the Peninsula? We have 7"-8" of snow in central Port Angeles - perhaps at 300' elevation. The wind is blowing fiercely and the snow keeps coming.

Anne Murray

Lindsey said...

If I'm understanding what I'm seeing on the radar, things are staying pretty far north compared to what had been predicted, and the whole thing seems to be moving east (or SE??) as it rotates its bands of moisture. Might be an interesting afternoon Seattle northward.

steven said...

Teresa,

In your post you mentiond "it's pretty obvious there's going to be snow".

Are you a meterologist? Do you have any training in weather science? Because if not I wonder on what basis you dare venture any opinion on the matter.

If so, please illustrate why you have such an opinion instead of throwing brickbats around like "ivory academic towers" or suggesting that scientists like Cliff Mass do not even bother to have conversations with "the pragmatists at the NWS".

Avalanche said...

2PM. McCHORD SOUTH WINDS AT 22 DP 32. BELLINGHAM NE AT 48 DP 0. OMG. CLASH OF THE TITANS!

Bryan said...

At least 8" in Port Angeles as of 2:30pm. Snowing hard. 23 degrees.
Strait (lake) effect perhaps?

MyronsWorld said...

Update 2:30p: Capitol Hill (Aloha/19th Ave E) = 1.75 inches. Snowing again. Could be a crazy unpredictable week ahead.

Joseph Ratliff said...

Bottom line, (2 - 4" or so) snow on the grass, almost nothing on the roads except water in Lacey. The water might freeze into ice, but I think we'll be A...OK. :)

Stay safe people.

Michael said...

Extremely intense shower/band of snow pellets just hit Normandy Park and Des Moines moving northeast, it was orange on the doppler and has dropped about 3/4" in about 30 minutes.

Very intense!

Josh said...

This is the difference between you and the National Weather Service (official) and why the NWS gets so much flack for being non committal on a tricky forecast. Not 2 days ago you said forget-snow-over-seattle-its-heading-to Oregon. The NWS always leaves a little wiggle room due to the fact that so many emergency agencies are listening to them. If the NWS had that same headline there would be some heads on a plater. Though they were hinting at the same forecast they were doing what you said forecasters should do in your book in the future of forecasting section. There is nothing wrong with sticking with your guns though. Sometimes you win some and other you don't.

Tanya said...

It's ok Cliff. I love the work that you do. You could have a little side of humble pie with your Thanksgiving dinner. :)
Also, the only way to forecast is to predict.

JewelyaZ said...

Three inches in Bellevue, blowing hard, 22F... and roads are a solid sheet of ice. Extremely dangerous... I abandoned my car (safely) in a parking lot and walked home with the two kids.