Thursday, February 24, 2011

How Good (or Bad) Was the Snow Forecast?


There have been some complaints about the recent snow forecasts in some quarters. The Seattle Times will run a story tomorrow "Forecasts for Snowfall in Seattle Goes Cold", several of you have commented about poor snow forecasting of this event, and even one prominent local TV weathercaster noted that sometimes he has to admit to making a mistake (about the snow over Seattle) and then proceeded to blame it on the models (and showed the UW model output for good measure!). Let me give you my take on this.

Before we evaluate the forecast, what actually happened. Well, the region did get snow and some locations a lot of it. Based on the official National Weather Service numbers, the heaviest snow (up to .5 to 1.5 feet) fell in a line stretching from Skagit County across Whidbey Island out to Victoria. On the northern Olympic Peninsula Sequim had 4.5 inches,Port Townsend 5 inches, and Port Angeles a bit over 9. Snow decreased toward Bellingham 1.5 inches and southward to Marysville (3 in) and Everett (4.5 inches). The immediate Seattle urban area had roughly .5 to 1.5 inches, with snowfall rapidly increasing to 3-9 inches on the eastside. Snowfall increased south of Seattle (Kent, Auburn, Southcenter, Sea Tac) to 4-5 inches. 3-5 inches from Tacoma to Olympia. Very little snow over the southern Kitsap Peninsula.

So it snowed, and in many areas it was appreciable. I5 was closed for a while near Mt. Vernon and crippled near Sea Tac last night.

Let us consider how the UW WRF model did, since this is important guidance to both the National Weather Service, local TV folks, and yes, even me. Let me show you the 24h predicted snowfall for the period ending 4 AM this morning for several model runs starting days ago. Let see how consistent the 4-km resolution model guidance was and how it changed in time. You be the judge!

Here is the forecast initialized (started) at 4 AM on Monday. Note the lack of snow over Seattle and the Kitsap (due to rainshadowing off the Olympics). Heavier snow north of Everett and over the N. sides of the Olympics. Moderate snow over the eastside communities and heavy snow over the mountains. NOT BAD!.


The forecast made 12-h later. Similar situation


In the forecast begun 4 AM on Tuesday, the Bellingham snow threat has declined. The Skagit snow band was there, the Kitsap-Seattle dry band is there but weakened. But too much snow was evident over North Seattle.

Twelve hours later a distinct snow band was positioned over Seattle. Clearly, not right.
And here is the forecast from 4 AM Wednesday morning. The Seattle snow band had weakened and heavier precipitation had moved north. Better, but not perfect, of course.

Now there are a few things you should take away from this.

First, the model (and the others the NWS and I were looking at) was serious about snow; although the snow distributions changed from run to run, they all indicated a serious threat. Second, they all agreed the mountains would be hit hard...and they were. Most of them showed a lessening of precipitation over the Kitsap and southern Seattle, and substantial snow over the eastern suburbs. Most indicated enhanced snow in some kind of east-west band, but the position varied. This was a crucial point....it was clear that the greatest threat was in a zone of convergence between northeasterly coming from the Fraser River Valley (and surrounding low terrain) and southerly flow moving up the Sound. But there was NOT agreement exactly where this would be. There was uncertainty for this feature.

It also turned out there was uncertainty about where the low pressure center controlling a lot of this action would be positioned.

To get this prediction right the forecast had to simulate all the following correctly: the downslope off the Olympics , the flow through the Fraser Gap , the position and intensity of the low , and upper level trough approaching the region, among other features. All interacting in a very non-linear way. And it was worse than that. Most of the showers were from convection--isolated snow shower that are very much hit and miss. It was clear there would be a lot of banding and variability in the snowfall. Folks, getting all this right is beyond our technology and science.

So was this forecast a failure? I don't think so. Even though we did not have confidence where that intense snow band would set up, we could tell you it could set up somewhere resulting in very heavy amounts. We could tell you the mountains would get large amounts and that serious snow would hit the eastside. We could tell you about the rainshadowing over Kitsap and Seattle as being a probable element. And the snow on the north side of the Olympics. We gave a modest snow range over Seattle (roughly 1-6 inches depending on whose forecast you looked at) to cover the uncertainty.

Will we eventually do better than this? You bet...and we are working on a technology at the UW (called Ensemble Kalman Filter data assimilation) that might do so, but this is a few years off. And the new coastal radar will paint out the critical flow structures offshore that we can't see now.

This snow forecast is a vast improvement on what we could have done only a few years ago. And a critical issue it reveals is the necessity for my profession to learn how to effectively communicate the uncertainties in our forecast. To paraphrase an erstwhile Secretary of Defense: we need to tell you about the known unknowns.

And in a future blog I will discuss the shameless and occasionally irresponsible hyping of this event by a few media outlets, including their breathless description of sudden icing that supposedly would befall yesterday's commute...just like Nov. 22nd! Complete nonsense.

50 comments:

amy said...

hey, we still have snow falling (light) and it's 10:29 on Thursday night....and have more than a foot on the ground (500 elevation) Port Angeles. I'd say your forecasts were pretty accurate.
Now, tell me it's going to warm up and melt quickly...

Mark said...

Cliff,

Appreciate your description of the events that unfolded and how they compared to the model runs from the previous days. I followed the weather discussion from the NWS from Sunday or Monday on and also Scott Sistek's tweets and blogs as well.

The 'sudden icing that supposedly would befall yesterday's commute... just like Nov. 22nd!' idea may have been complete nonsense but the NWS discussion from the day before the event mentioned the same idea. Could have been where whoever was 'breathlessly describing' it got their info

The 312 PM PST TUE FEB 22 2011 NWS Forecast Discussion written by Albrecht included this...

12Z MODELS WERE RATHER IMPRESSIVE WITH SNOWFALL AMOUNTS OVER CENTRAL
PUGET SOUND DURING THE DAY WED. THE 18Z RUNS INDICATE 2-6 INCH
TOTALS FROM ABOUT ISLAND COUNTY SOUTH TO TACOMA...WHERE CONVERGENCE
FROM THE DEVELOPING UPPER TROUGH DEVELOPS. THE ARCTIC FRONT RAPIDLY
SHIFTS SOUTH INTO THIS CONVERGENCE BAND IN THE AFTERNOON. THE
AFTERNOON COMMUTE MAY BE QUITE INTERESTING AS TEMPERATURES FALL INTO
THE UPPER 20S. A FLASH FREEZE SIMILAR TO THE NOVEMBER 2010 EVENT IS
NOT OUT OF THE QUESTION.

DJ said...

Well, at least they are more accurate than The Vancouver, BC, Canada forecasts. The forecasts generated by Environment Canada are computer spit out garbage. Almost no human interaction, no synopsis, no nothing.

Victoria BC got slammed with up to 30cm (11 Inches) of snow and Environment Canada didn't even post a warning until the event was nearly over. Not even an advisory was issued. It is pathetic up here in Vancouver.

We often rely on the forecasts given for Bellingham or Blaine. We also depend on the forecast discussions issued by the National Weather Service since Environment Canada sucks so bad.

So it's not all that bad for you guys down there in Washington and near Seattle. It could be way worse! You could be up here, and have NO idea what the weather is going to be like!

mimi said...

don't let those haters get you down, cliff. keep on casting. forever.

climo man said...

I don`t have too much of an issue with the snow forecast,although I feel that there always is a tendency for the NWS to underestimate the potential snowfall in the Snohomish-Skagit county areas prone to CZ`s.
However, I do have concerns about the accuracy in temperature forecast in these kind of winter events.I feel that the NWS should factor in wind direction and speed, snow cover, and length of day more in their temperature forecasts.For example, the 19 degree minimum forecast for Seattle seems about 5 degrees too low, considering the virtual lack of snow cover in Seattle, and especially, the fact that the wind direction has been consistantly out of the east or northeast today.Any easterly wind direction always prevents any temp drop at Sea-Tac.Also, the 33 degree max predicted for Sea-Tac seems quite low considering that the day length is now two hours longer than in December,which means more solar heating.It would take a pretty stiff northerly breeze to keep the max temp that low.Conversely,in wind sheltered locations where the snow cover is deep, I would not be suprised to see minimum temps colder than what is officially predicted.

Kevin said...

As I'm sure you've heard before, I'd rather be warned of a possibility of a heavy snowfall in my area and have it be wrong, then not be warned and then dumped on.

But as for the news hype: Sno-My-God(TM)! Someone needs to give those people a chill pill.

smokejumper said...

Right on for mentioning the convective nature of the showers.

I'm not calling it a bust here in E. Wash. because models did well but such a liberal use of warnings. Well needed in Spokane to Pullman, got pounded w/ foot plus. But lower basin, lower slopes, majority land wise few flakes.

rich said...

The issue for me was the National Weather Service's issuance of a Winter Storm Warning for the Seattle area. If there was so much uncertainty, the NWS shouldn't have issued that, as the criteria is the probability, not the possibility, of heavy snow. Or maybe they should have qualified it more.

Carrie Bowman said...

Whew! Thank you. One request: choose a role model other than Rumsfeld. He has the unscientific habit of arbitrarily choosing what he knows or does not know and did not as Sec of Def (in my opinion) intend to tell us what he knew was unknown. I hope atmospheric scientists choose a different, more honest path!

Colleen said...

I don't believe the forecast was terribly off-base, but the ongoing winter storm warning in Whatcom County served no good purpose. There was never a need for a warning in the first place. I'm hard-pressed to find anyone in my area who takes such a thing seriously because it's inevitably wrong.

Cliff, you mentioned "the shameless and occasionally irresponsible hyping of this event by a few media outlets". I don't listen/watch those outlets, but I can imagine. The reality, though, is that they're serving a hype-hungry audience. The less our society actually interacts with nature, the more we're fascinated by "nowcasts" and such. Ironic.

Pen said...

Thanks, Cliff.

I for one was very pleased with the forecast. Maybe it's because I live smack dab in the foothills and we always get dumped on. Yet this is NOT always the case. Every now and then, we dodge the bullet.....sometimes this is forecast, many times not. As far as I am concerned, forewarned is forearmed.

We used to live in Seattle where snow is more of a novelty. Out here it can be a serious matter and I would rather know what is possibly coming, than just whether the kids have a day off school or not. BTW, my kids go to school in the city...a 45 min. drive door to door. It is up to my discretion whether we attempt to get them in or not depending on the forecast. Again, better safe than sorry. Luckily (or not, if my kids get a say), they were off this week for winter break. There is no way I would have driven them in today, and if school was open, I probably would have picked them up early on Wednesday. I've been caught on I-90 for hours a few times.

In fact, in November, when we had that bad storm and ice up that caught us all by surprise, after your prediction and NWS, I grabbed them out of school at noon. I was home and safe, getting calls from friends who had picked their kids up at 3;30pm and where still trying to get home 5 hours later...some lived 5 miles away from the school.

So I say THANKS! Between you and the NWS, we are usually safe and sound at home when we need to be.

Alpine Lakes Aficionado said...

While I am very disappointed with the snow fall at my house, I feel like the forecast was pretty spot on. I think it was clear that we would have snow and it would be highly variable depending on location. It seems like it was expressed that we would have clearing and very cold temps as an aftermath which again is spot on. I do think that the transition may be messier than predicted however.

E

froggie farmer said...

Goes back to the old phrase: "you can please some of the people some of the time, but you can't please all of the people all of the time." The work you're doing to move this science forward, and the effort you make to communicate what scientists know and do not know, is already "above and beyond the call of duty." There will always be folks who poke at any mistakes we make or uncertainty we have. It's their way of making themselves feel superior and it's a shame they have to resort to that, particularly in public venues. Please know that there are many more of us who appreciate what you do, and how challenging your predictive work is. Keep up the good fight. It is appreciated for what it is - one part science, one part intuition, and one part sharing. That's the best any of us can do.
Kathryn Kerby, Snohomish

Fred said...

Cliff- Thank you for this excellent hindcast and analysis. Like it or not, the responsibility here is to prepare for the worst, and the responsibility is for the forecast AREA, (not just Seattle). From my perspective, things were handled pretty darn well, (though I don't watch, and can't speak for, TV wx).

John said...

As someone who has lived in the Seattle area my whole life, it's always been notoriously difficult to forecast snow because of all the factors contributing to weather conditions. I actually found the weather predictions from this blog to be very useful. Living in Poulsbo, I got what was expected: mild precipitation. Watching the models change as conditions change is also quite useful. Keep up the good work.

Steve said...

Hey Cliff,

Your models predicted 1.5" at my house in south Kitsap. We received 2.5". The sky is falling!!!!!

Good job, and thanks for all your time you volunteer to try and keep all of us PNW ninnies happy!

SuperG

mjgrota said...

What did the Farmers Almanac predict?
Thats the real test!

Tim said...

in thirty years we will be complaining that we have to take our clothing in for repair because it malfunctioned when it didn't synch with the models and accidentally went into rain mode instead of snow mode.

Heather said...

People are complaining about this snow forecast? Really!

I thought the forecast was very good. There was snow over much of the area, including in low-land urban areas. Isn't this exactly what was predicted? It is just ridiculous to expect an exact prediction of how many inch of snow will fall on your driveway.

But maybe I got a better forecast than most people because I checked only Cliff's and NWS's forecasts. I didn't pay attention to any commercial forecasts.

HarrisonCZ7 said...

"And those have every right to be upset with the blown forecast. It is our duty to try to get the best forecast we can and when we predict 2-5" and something close to squat happens, we didn't do our job and we will learn from this." -Scott Sistek.

That's Scott Sistek on his blog. Interesting comments. I definitely think they did do their job. We were all informed of the potential for heavy snow. As you said, we'll have to learn to live with some variability in the forecast. Ultimately, as snow lovers, I think that's one of the hardest realities we'll have to accept. By are very nature, we dislike uncertainty.

"The less our society actually interacts with nature, the more we're fascinated by "nowcasts" and such."

Colleen: This makes no sense. How would 'interacting with nature' somehow decrease my fascination with NOWCASTS?

Well done overall Cliff. Your blog entries always serve to inform. Thank you!

Houseboat guy said...

I think your forecast was very good. People can't seem to see beyond the length of there nose and take in the big picture. You said it was going to snow and it did.... and when you said it would . You said it was going to come in varying intensity and exact locations uncertain. Timing was more or less right, temp's were more or less right......... What's not to like?


Many people fail to understand the complexities of weather here in the northwest. Its a hard place to forecast whether in the best of times let alone Exactly how much snow will fall in someone's driveway tomorrow..... and god forbid you get it wrong by an inch or two....

It only snowed 1/2 an inch here in north Seattle, but i realize you don't have to go more than a few miles to get a lot more snow...... Shame on you for not predicting that cloud over my house. How could have you miss it?

There are people who will never be satisfied no mater how accurate the forecast gets.

LOVE your blog Cliff...I know kids that read it every day and have taken scientific and rational interest in local whether and now giggle at TV whether guys. I bought one of them your book and she loves it. ......... Keep up the stellar work!

Bill

Colleen said...

Proving once again that we all have different experiences, we feel just the opposite of DJ, who derided the Canadian forecasts. In the 15 years we've lived here on the WA-BC border, we've found those predictions far more accurate and useful than anything generated on this side of the border. With the notable exception now, of course, of Cliff's blog. I consider this my own reliable source ~ and even when Cliff's not spot-on, he presents the info in a thoughtful, intelligent manner. Can't beat that.

HarrisonCZ7, actually being in the weather means you know what's happening firsthand. Much of our society now spends the vast majority of their time inside, yet they want constant, immediate updates on the weather. That's what I find interesting.

Jeff said...

I found your forecast and info very helpful. It was exciting to see the convergence-caused arc of heavy snow set up running from Redmond to Des Moines and know what I was looking at. It also gave me confidence that I would be able to get to downtown Seattle to pick up my wife from her job at 8:00 PM and be able to get back home in the Central District.

So while snow at home in Seattle was a "bust" the road conditions at work in Seatac the next morning were described by employees who made it in as "taking your life in your hands".

From that I can see how someone in Seattle would describe the forecast as crackers while people in the south and east would find it "spot on".

MaggieNo said...

I was stunned to hear about the forecast complaints. Perhaps too many of the people are newcomers from other parts of the country where you can call relatives a few hundred miles to the west, ask about their weather, and be nearly 100% sure that the same weather will be over your head in a few hours? I grew up in Cleveland, OH, and that's the way it worked for us: we'd just call Fort Wayne, IN, and prepare according to their experience.

After 40 years in this area, and as s gardener, I can attest that although the forecasts have gotten incredibly better, there's no such thing as a guarantee for local weather.

Colleen's right: people seem increasingly disconnected from natural cause and effect. I hear complaints about rain -- in November even! And people complain about how cold it gets on a sunny day in winter; no sense of the value of cloud cover at all. Seattle's mild climate needs our misty, wet days to stay green over the summer, and all those clouds to keep our winters cozy, not desperate.

Teresa said...

The sudden icing was NOT complete nonsense. Just because it didn't happen in Seattle, it doesn't mean it didn't happen. I don't know details of other areas. However, in Sammamish, people were abandoning cars on Sahalee Way, the main hill getting into our community, by 6:30pm on Wednesday. Highway 202 was a parking lot. Seattle Times reported that roads in Snohomish County were a sheet of ice by the morning commute, and very possibly had been that way all night. South Seattle and Tacoma had traffic crawling.

I applaud the news for being less Seattle-centric than usual.

Seattle didn't get much snow by commute-time. Those who DID get snow had icing up problems.

http://www.kplu.org/post/thursday-mornings-headlines-10

Brian said...

Snow amounts can change so much in just a few miles. I live in Bellingham, or I should say, just a few miles east of Bellingham (officially I do not live in the city, but my mailing address is Bellingham), and we got 6 inches of snow. In the city, maybe an inch. Even a few miles to my north had only 2-3 inches.

Of course, had this been rain, nobody would be complaining that they got .4 inches of precip instead of .6, or 1" of precip instead of .4. Nobody notices or cares when it is rain.

LVDLM said...

What strikes me most strongly (as an old man; my handle acronym expands to "le vieux de la montagne")is how much forecasting has improved over the last generation. As recently as, oh, 1990, I would set off for an outing in the hills disregarding the forecast, figuring that if I stayed home both when the weather was forecast to be bad and when it actually WAS bad, I'd miss most of the rare good days. Nowadays, the UW models and the NWS forecasts enable me to save time and money and avoid much misery by adjusting plans to match the prognosis. (It's actually often the case that decent weather is to be had somewhere not far from Seattle, and now, thanks to the modeling improvement, it's possible to find it--a day or so in advance.)

A bit more ranting: The United States enjoys roughly a fifteen-to-one advantage over Canada in its ratio of land area to taxpayers. So it's hardly surprising that Environment Canada may to be struggling--not only with its forecasts but also with its 1:50000 topographic maps, for example. And if topography complicates the forecasters' lives in Puget Sound--as we all know it does--BC is close to the ultimate nightmare.

Last, we who live in the US and especially in the Northwest are the lucky ones. I've been told that Canadian forecasters are enjoined from making public their equivalent of the AFDs (the NWS acronym for forecast "discussions"), which are invaluable south of the border partly because they DO communicate the uncertainty in the forecasts. And while Europe may produce a more accurate global model than our North American counterparts (think how many taxpayers per model run support the ECMWF), the results are generally hidden from the public, whereas we can freely see our forecast products as fast as they're generated. Oughtn't we to be grateful for good government?

And most important, the UW's research program and especially the Consortium give us in the Northwest a huge advantage in available information over our friends in other regions. (Hint: there is a way to support this effort, on Cliff's blog page.)

Finally, perhaps those who depend on TV for news and weather deserve what they get. If you know someone suffering from dependency, you might recommend http://www.turnoffyourtv.com/.

Deborah said...

If Seattle had been hit the way Port Townsend was on Wednesday afternoon, with several inches of really sticky snow, folks would complain that they weren't adequately warned.

Ferdi said...

While forecasting specific snow totals for specific locations is still darn near impossible, I would like to point out how amazingly accurate the long range prediction for this event was. Last Friday I looked at the 180 hour weather model loop. From this I could see that Wednesday to early Thursday provided the best chance for lowland snow in our area. For a forecast 5 days out this is really remarkable. Forecasts will always be couched in probabilities and frankly I hope we never remove all elements of surprise from our weather. As you say Cliff, the forecast was right for most of the area. It certainly nailed it for my neighborhood. They do need to iron out some communication issues such as wind speeds for the San Juan Islands as opposed to the Northern Inland Waters. These should be the same. And perhaps we should level the Olympic Mts. and do away with that darn snowshadow.

Niko said...

Colleen -
While it wasn't needed for most of the county, there were definitely areas in Bellingham that did get 4-5 inches. And these locations happened to be just a few miles away from those places which got 1-2 at most. So some kind of winter weather advisory was good (as of last night, our main roads were still covered with compact snow), if for nothing else but to cover those higher ends. Better more prepared than not!

Connie said...

Cliff, I've been linking your forecast into my Facebook wall all week to combat the "sky is falling" broadcasters.

Having grown up in Saint Louis the weather there was pretty straightforward. We'd simply look at what was happening west or south of us (occasionally north) and know we'd get the same in about 4 hours.

I appreciated learning about your blog because now I understand the convergence zone better, and can put some perspective on the other reports I hear/view.

Jonathan said...

What is the big deal if you are off a little bit? Why get so upset about this stuff? It does affect travel, but snap out of it complainers. Move on with your life, unless you just need something to get angry about. Think back to twenty years ago and the kind of forecasting we had then vs. now. Keep doing great work Cliff!

Erika said...

Well, okay, I guess it sounds like the forecast wasn't very accurate for Seattle. But not everyone served by the Western Washington news outlets lives in Seattle!

I live outside Deception Pass, and the forecasts were dead on. Like, ridiculously correct. That never happens!

I'm glad for it, too. Having received advanced warning, I went grocery shopping on Monday and stocked up on supplies, fresh produce, etc. That was the last time I was able to leave home... getting a little stir-crazy out here, but at least I have plenty of coffee!

bloglogger said...

@froggie farmer re:

'Goes back to the old phrase: "you can please some of the people some of the time, but you can't please all of the people all of the time." '

The old saying is "You can fool some of the people all of the time, and all of the people some of the time, but you can't fool all of the people all of the time."

I guess it can be applied to pleasing as well as fooling.

Lansing said...

separate topic (nonetheless about forecasting). care to comment?
Thank you, Cliff.
http://www.zerohedge.com/article/why-pacific-decadal-oscillator-means-five-more-years-very-bad-fed-luck

TVN said...

Here's a random question about the hindsight of forecasts. I've always been very curious about the LACK of the forecast of snow with the November 2006 storm. As far as I recall, there was NO hype or warning and it took me four hours to drive four miles home. How exactly did that storm unfold and why the lack of foresight?

Stands in contrast to this last event.

Josh said...

Colleen has come upon something. I wonder how many people were watching the UW radar loop, nowcasting on their iphones,and refreshing their NWS pages as the weather passed by outside." Virtual Reality Storm Chasing"

When working a large fire incident we have our fire mets (meteorologist) get out from base-camp and drive the fire ground to get "situational awareness" of all the local things that can drive the weather.

Yes the forecast was pretty dot on.
I don't want to be in the NWS shoes though. They play a fine line. Unlike Cliff who can go out on a limb and say this is serious, the folks at Sandpoint are "official". Their bulletins can change the outcome of life and safety and can even be used in litigation.

Cliff you did great on the forecast though.

KurmudgeonlyYours said...

Good Grief! It's winter. There are impediments to perfection. Forecasting is a good as it can be given the lack of coastal radar and the big rocks to the west of us. The yellow jackets and now the blue jackets on 4 have a job to pull us over to their stations - and they do by taking the worst case scenario and throwing it at us to get excited about. I don't think you have to explain yourself or your process. No, I'm not an academic. I just enjoy reading your information because it is NOT sensationalized as with the media. Keep on doing what your doing. You make a different in forecasting.

JewelyaZ said...

Sort of off the topic, but sort of not, Cliff... I see that the models are changing on Probcast... can you write a post about how, and what that's going to mean for (loyal, dedicated, need-to-send-money) users like me?

Is it going to get better at low temps in cold weather? That's its weakest link; I usually laugh a little over that number. Last night, for instance, for 98008 it said 17 and 10% chance as high as 22... I called 22... it was in fact 21 at our house and at the official SchoolNet Phantom Lake station 0.8 miles away.

Since the REST of Probcast is so fantastically useful, I don't sweat the low-temp issue too much, but I'm very curious about potential improvements there.

Thanks for all you do!

John Marshall said...

I was on my boat in Anacortes when I saw the Tuesday 9am forecast, and instead of waiting until Wed morning to come home, I immediately left Anacortes to head back to Sequim Bay. We barely got there on Tuesday afternoon before snow showers began.

We got up to our house at 1200 feet (top of Bell Hill) and had 14 inches of snow. Had an upslope due to the NE winds that gave us a "reverse rain shadow" at that elevation.

Forecast was OUTSTANDING in that it told us to get off the water and home before it hit.

Only thing that was off were the winds forecast for east Juan De Fuca. Winds did not reach gale force as predicted.

John M

Wx Enthusiast said...

Similar to Erika's comment, people should also realize that the National Weather Service office in Seattle also forecasts for more than just the Seattle metropolitan area. Their forecast area covers from the coast to the ridge of the Cascades, and from the Canadian border to Toledo (technically, the southern borders of Grays Harbor and Lewis Counties). Yes, they do issue forecasts for specific parts of the area, but their discussions are written for their entire forecast area.

In addition, their watches and warnings for winter events are issued by zones that are larger than your specific neighborhood. For example, the lowlands of King County west of Lake Washington (from Shoreline to Federal Way and everything in between) are one zone; the rest of the lowlands of King County, including all suburbs east of Lake Washington, are another - the East Puget Sound Lowlands. If their criteria is expected for even just one part of the zone, their warning is issued for the entire zone. For example, the snow along the arctic front was expected for some part of the zone, so even though there was also expectation that some areas would not see much snow, their winter storm warnings were in effect for the entire zone. Another (non-snow event) case where this is very noticeable is in the case of strong easterly winds in the Enumclaw/North Bend areas, when wind advisories or high wind warnings can be issued for the entire East Puget Sound Lowlands zone, but most suburbs close to Seattle but east of Lake Washington don't experience much wind even though they are in the advisory/warning.

Those thins said, most of the lowland warnings for the Portland area were not accurate, much more so than in the Seattle area. As late as Thursday morning, NWS Portland was mentioning in their discussion the chance of 3-6 inches across the northern Williamette Valley later that morning, due solely to an isolated model (the NAM) bringing the front south too soon, causing strong easterly flow through the gorge and meeting a surge of moisture from the Pacific across the area. It was an isolated model solution and did not make a lot of sense. Alas, most of the lowlands across the Portland area had an inch or less of snow, and many places had nothing. The frontal passage, as indicated by most models, was almost completely dry. Temperatures rose into the upper 30s yesterday, any small accumulations Wednesday night melted quickly yesterday morning, and people involved with schools all around the area wondered why they canceled instead of going on two hour delays. In the case of the Portland area, there was really no point when the models in general, particularly the GFS and WRF-GFS, were showing much in the way of accumulation there.

Wx Enthusiast said...

Hope you enjoyed the anticipation and excitement of the snow. Now we get back to weather boredom for at least another couple years.

Christopher said...

I agree that the models were about as good as we could expect -- heck, when I was growing up it was all the forecasters could say to say that we might or might not get some snow tomorrow or the next day.

But, Cliff, here's a question I hope you'll address. For those who really want to get the most accurate, unhyped information about the coming weather, after we have read your blog, which as you point out is NOT intended to be a forecasting blog, what sources do you recommend that we pay the most attention to? We have lots of options. Three local TV stations. Many local radio stations. On the Internet, we have the Western Washington Zone forecasts, which generally seem to come out twice a day. We have the NWS Area Forecast Discussion. We have the NWS Point Forecasts (which in my experience do a lousy job of forecasting wind speeds in their hourly graph format). We have Accuweather, Weather Underground, and Weather.com, all offering almost hourly predictions of temperature, precipitation, dew point, wind speeds, etc. We have all the various offerings on the GFS-Initialized Pacific Northwest WRF Weather Forecasts, not to mention the other options on the Pacific Northwest Environmental Forecasts and Observations page. We have the NWS Graphical Forecasts based on the National Digital Forecast Database. And I'm sure there are lots of others I haven't found. But if you had to pick two or three sources that you would recommend people look at to have the best chance of getting a reliable, as-accurate-as-possible forecast, what sources would you recommend? Inquiring minds really, really want to know!

Christopher said...

Colleen wrote: "Proving once again that we all have different experiences, we feel just the opposite of DJ, who derided the Canadian forecasts. In the 15 years we've lived here on the WA-BC border, we've found those predictions far more accurate and useful than anything generated on this side of the border. With the notable exception now, of course, of Cliff's blog."

I have to agree. We are much closer to Victoria than to Seattle, and I tend to find the Victoria forecasts better than the Seattle ones, or even the point forecasts. Victoria is usually the first site to forecast wind events, and they quite often get it better than the NWS Zone forecasts do. What I miss, though, are the timing details and discussion -- those are better from the US forecasters.

Meilir said...

I followed you and Scott Sistek closely from last Sunday onwards. Both forecast commentaries were excellent (especially yours). You both mentioned the effect of the snow shadow and you in particular emphasized there would be no flash freeze.

The pattern of weather you both forecast was very accurate. It seemed to me that only the origin of the (x,y,t) coordinates was a bit wobbly - but what the heck.

Well done!

Renton

Michael Winter said...

What strikes me about the model data was how the models became less accurate as the events got closer.

Normally you would obviously expect to see the opposite. The central sound was modeled very well 60-72hrs out. The next model runs just did worse and worse until 24hrs out at which point it improved but was still not catching the subtleties right. Wonder why the data on subsequent runs caused the central sound modeling to be so far off.

Zathras said...

The NASA highres satellite picture today shows the areas that did not get significant accumulating snow.
http://www.facebook.com/photo.php?fbid=113258458751291&set=o.122498337810581

if that url does not work, here
is a wider shot 1km res
http://rapidfire.sci.gsfc.nasa.gov/subsets/?subset=USA1.2011056.terra.1km

Personally, I think cold advection
and westerlies are bad for Seattle (obviously very good for snow just about everywhere else) warm advection however with westerlies I think sometimes works out for snow--I'm talking about east of Hood Canal, see the images. But it may just be that more moisture in warm advection overwhelms the downslope drying effect. Saturday night will be a good test for the 4km solution.

Anyway, not the dry area where the cold dry Fraser air must have kept the snow showers at bay in the photos.

Will said...

Dear Cliff,

As a commuter from Phinney Ridge to the North Creek valley my observations are 1)

Thank you very much for this blog!

Paul said...

Dear Professor Cliff,

I really enjoy following your blog and would appreciate it if you also discuss about the issues and strategies of communicating meteorological information to the non-scientific public audience. Working in health services research I know that we academicians can do a better job at risk communication (or just plain communication?). I even find it difficult myself to explain to a co-worker what a 95% confidence interval is. Thank you so much in advance!

saros said...

A few flurries this morning on San Juan - we had 2-6 inches depending on location (west side got the most), but it's warming up now.

Do you think there'll be any more Frasier Gap events this winter??