Sunday, February 8, 2009

Weak Front, Colder Air, and then Hood Canal Snow

Yesterday, there was bright sun in the mountains, but the low clouds and fog held in the southern Sound for most of the day--with Seattle northward breaking out in the early afternoon. The trouble this time of the year is that the sun is not strong enough to effectively mix out the nighttime inversions that often form under high pressure conditions. The low clouds are also self-maintaining--since they reflect the feeble winter rays back to space and the cloud tops are effective radiators in the infrared (and thus promote cooling). In the spring, the sun is much stronger, daylight is longer, and the atmosphere is less stable...allowing more mixing out of the thin veneer of cold air.

Today a week front is approaching the coast and the high clouds associated with it are already over western Washington (see satellite picture). The mountains are relatively cloud free and low clouds fill the basin of eastern WA. Current radar indicates dry conditions over the interior, with a few showers to the west (image). Today should remain dry and with the low clouds dissipating over most of the area..there will be some filtered sun for many. As the afternoon progresses, the clouds should thicken and lower...and showers should occur tonight for most.

Tomorrow, there will be some residual showers...mostly over the mountains and in Puget Sound convergence zone. The air aloft will cool substantially...opening the door for some mixed precipitation on Tuesday.

Tuesday will be interesting...a stronger frontal system will approach in the afternoon. Cool, but not cold, air will be place. Places of higher elevation (above 500 ft) and where heavier precipitation occurs (SE of the Olympics) could see some snow. In fact, the computer models are indicating several inches over Kitsap and SE of the Olympics..with some snow shower extending east to some higher elevation areas (see figure). The models also sugget snow over SW Washington...south of Olympia. As the system moves in the air will warm and precip will turn to rain in the lowlands. So the salt trucks may not be needed! The mountains will pick up several inches of snow...but they really need much more to make skiing fun again.

Heading up to Bellingham soon to give a talk at Village Books at 4 PM--general intro to NW Weather.

Finally, there have been a lot of interactions about the comments section. Let me ask those who are making comments a favor:

1. Stick to weather or its impacts
2. Please no editorial comments about wording or grammar. A few (a suspect a very few) get hot under the collar about my use of words like "nice weather." If you don't like my use of language go to another blog.
3. I can't answer all the questions, all the time...I simply don't have the time. Please understand.

39 comments:

Shane Robinson said...

Thanks Cliff. A question if/when you find the time: Are we near a record for seasonal lowland snow this year? I imagine that could be measured in number of days with snow or total accumulation (or snowfall), but I cannot remember a season with so many days with snow in the forecast.

Thanks for all the work you do, and the information you disseminate.

Bob said...

I read what you post and attempt to extrapolate, using our regional forecast, what we may see here in the Upper Columbia Basin. Keep on blogging in your style – “it’s who we are.”

Bob

Anonymous said...

Thank you for your efforts Cliff
Leif Knutsen here. Question: I have spent a lot of time boating and have noticed that the high winds often seem to decrees around a tide change. Is this a grounded observation or similar to a full moon causing more accidents? If so, why? Do high winds correlate to big tides?

Anonymous said...

I liked those rain graphs, any chance we could see a tempature one ?
It sure seemed like it was much cooler than normal the last 3 months.

Tim Pritchard said...

Any thoughts on the accuracy of weather.com's 'new' TruPoint analysis?

http://www.weather.com/encyclopedia/trupoint.html

Thanks - keep up the great work - it's very much appreciated!

climo man said...

Shane:
This season (so far) pales in comparison to the great Seattle snow winters of 1915-16 (60.9 inches), 1949-50 (63.6"), and 1968-69, (67.5").This winter could be considered a "honorable mention" year, along with 1985-86, 1971-72,and many other earlier seasons in the 20 to 30 inch snow total range.

I`m still quite skeptical regarding any major snow on Tuesday.We seem to be right in the focal point of the split- the front is breaking up right over us, with most of the action going south, and a little north of here.I think the bulk of the cold offshore trough will get deflected south,and we`ll not get enough cold air, nor sufficient outflow to pool up on the lee side of the Olympics as the models suggest.

Anonymous said...

climo man...i don't recall 85/86 being that big...got enough snow to sled on, but it seemed like about 5 inches in seattle. ...no more...??

Anonymous said...

The Seattle office recorded about 10 inches in Nov. of '85; and the SEA office recorded about 17 inches in Nov. of '85.

Franz Amador said...

I'm fuzzy on why winter sun should be weaker than summer sun. When the sun's at, say, 60 degrees above the horizon, is it really sending in less energy in February than from the same angle in July? If so, why? The difference in distance to the sun caused by the earth's tilt seems like it should be insignificant compared to the radius of the earth's orbit.

WeatherNerd said...

Franz

I'll try to answer your question.
In the winter the sun is much closer to our SOUTHERN horizon for the entire day compared to say in June when it is the furthest from the SOUTHERN horizon for the entire day. Have you noticed the sun is nearly directly overhead in mid June while this time of the year it is staring you in the face as you drive southbound on I5. That angle moves slowly throughout the year and helps create the difference for our temperatures. The sun "emits" the same amount of energy toward the earth but with the suns rays at the lower angle they "skip" over us more. An analogy of sorts: when you skip a rock on a smooth lake small ripples are left on the surface. Whereas if you throw a rock high in the air and it hits the water the ripples would be much greater. The difference here would be the amount of energy absorbed by the water, in the same way the suns energy hits the earth. The earth's atmosphere (in our neck of the woods) absorbs much less energy in the winter as does in the summer, therefore our temps are much lower. And you are right, the distance we are from the sun does not impact our temps much, if at all. In fact, the earth is closer to the sun during the winter of the Northern Hemisphere.

WeatherNerd said...

I remember the snows of the 85-86 winter. In November we had an extended period of cold weather with at least 3 days of decent snows. I lived in Renton and had accumulated 8 or so inches of snow over a couple days, then had almost another foot on top of that in one dumping a few days after that. A fun time for me while in grade school!

Anonymous said...

I remember the 85' storm. It was several inches of snow and highs in the 20's with a pretty good north wind. I rode my bike in it and didn't slip, sans salt and all.

andycottle said...

Not to bad of a day here, and was an alright day weather wise, though cool. High a high of 47 with low of 29. Though did have some thick morning fog which turned into an overcast day with filtered sun.

Say Cliff....any chance you`ll be doing any talks over in the Redmond area anytime soon?

. said...

More for Franz:

Summer sun = high overhead sun at noon.
Winter sun = noon sun is lower towards horizon.

Our atmosphere absorbs & dissipates the suns energy. Sun overhead = less atmosphere between us & the sun. Sun lower on horizon = more atmosphere between us & the sun.

Sun overhead = more energy reaches us. Warmer temps and more sunscreen.

Sun lower = less energy reaches us. Cooler temps and less sunscreen.

. said...

Cliff!

You're great. We love ya man.

Don't fret about the commenters. There are far more who value your posts than those who want to absorb your energy.

Just give us what you're willing and able to share. The rest will take care of itself.

climo man said...

Trivia note: Sea-Tac AP has only had 0.50 inch of precip the last 31 days.If this current dry stretch had begun just one week earlier, this January would have been the driest in station history.( Timing is everything, climatologically.) Seattle January/February monthly precipitation totals in the 0.60 to 0.70 inch range are climatologically expected to occur approximately once in every 200 years!I don`t know what exactly the probability of a 31 day period
this dry that spans parts of two months is (maybe a NWS or UW ATMSCI statistician can tell us), but I`m almost positive that it`s something that might only occur once or twice in one`s lifetime.

Cliff Mass Weather Blog said...

Franz,
Image a flashlight shining on a table. Directed directly downward perpendicular to the table the circle of light in small and intense...this is summer. Now shine the light at an angle...the circle of light is broader and less intense..that is winter. The radiation from the sun is thus more intense in the summer..which leads to greater warming. Strangely enough we are closer to the sun in winter than in summer (N Hemisphere)

Regarding the snow...I don't expect a megaevent..just snow in the mentioned areas..turning to rain.

Finally...no reason to expect tides and winds should have any connection....

..cliff

Cliff Mass Weather Blog said...

Franz,
Image a flashlight shining on a table. Directed directly downward perpendicular to the table the circle of light in small and intense...this is summer. Now shine the light at an angle...the circle of light is broader and less intense..that is winter. The radiation from the sun is thus more intense in the summer..which leads to greater warming. Strangely enough we are closer to the sun in winter than in summer (N Hemisphere)

Regarding the snow...I don't expect a megaevent..just snow in the mentioned areas..turning to rain.

Finally...no reason to expect tides and winds should have any connection....

..cliff

Jason said...

Thanks for your blog, Cliff! Good and relevant information for us weather junkies and it is appreciated.

Anonymous said...

Teresa in Sammamish: Thanks for the snow info Cliff.

And as usual with blogs, I like the commenters almost as much as the post. The sum total makes a blog work.

andycottle said...

Wait a minute here Cliff...

You just said we are closer to the sun in the in the winter than Summer? That can`nt be possible can it? I don`t see how. If this is true, then it seems like our days would be longer in the winter.

The idea that everyone about the seasons that we all know about is that in the winter, we are more or less turned away from the sun and thus...colder/ shorter days. Anbs summer, we are turned more or less toward for warmer/ longer days.

Josh said...

The seasons have nothing to do with how close we are to the sun. It has to do with which part of the earth (north or south) is tilted toward the sun and which is tilted away. We ARE closer to the sun in the winter than the summer, but the difference is negligible.

Also think about it - the southern hemisphere is closer to the sun in their summer than in their winter. If distance from the sun had anything to do with the seasons, then both hemispheres would have to have winter at the same time and summer at the same time...

Anonymous said...

It seems that Cliff will never answer any of the questions about the terminology because he doesn't believe that weather is nice. Sadly, extremely few people in the meteorology field actually do. Case closed.

andycottle said...

Well still, it seems weird that we would/ are closer to the sun during the winter. It just doesn`t seem right!

Anonymous said...

Yea Andy, I know what you mean...but it's the difference between 91,399,727 miles on January 3 and 94,508,727 miles on July 7 (approximate dates, they vary slightly each year). Not anything we would even be able to notice. :)

Alex said...

So all that really matters is the angle of tilt, not distance to the sun?

Anonymous said...

According to what I'm gathering yes, all that matters is the angle of the tilt, not distance. And anon is right, when the distances are that far what's a measly 3 million miles :)

JewelyaZ said...

Are any of you home weather station buffs? I got one for Christmas and I am having some weird readings, trying to figure out what the heck the problem is. One night I got a "high wind gust" of 114 mph, another I got a gust of 117 mph, and last night, I had a "high gust" of 54.something. These are all bogus readings but I can't figure out what's causing them.

The instruments seem to be mounted correctly. Any ideas would be MUCH appreciated.

We've had 0.00" of rain here in Phantom Lake, Bellevue, since I set the thing up. I was so excited about the little self-emptying rain gauge that you know the drought is all my fault! LOL Nothing like a little magical thinking to explain weird weather. :-)

Anonymous said...

Well, it is now snowing quite heavily in Kingston, with accumulation, and has been for about the last hour.

Mike of MLT said...

Classic PSCZ, and rather cold air aloft coming in. At 1am Point No Point is NW20G30kt while
Alki is South 19G31kt. And West or WNW winds aloft which favor PSCZ.
At the moment the precip is more organized than the meso models showed, and the NWS NAM model is a better match to the radar. The NAM shows the PSCZ persisting til about 7am, then getting skinnier and moving more over King county with the heavier precip around Carnation after daybreak. We will see.

Anonymous said...

Snow continues in Kingston. It is very wet, and the accumulation is very slushy (and minimal, maybe a quarter to a half an inch), but it has been falling for about two hours now.

Anonymous said...

It's 3:18 am and snowing in Lake Forest Park. Big, thick snowflakes sticking, about 40 degrees at 500 feet. My car is covered and there is about an inch of snow on the ground. After reading yesterday's blog, it looks like the weather has once again surprised some of us. I had heard maybe some snow and ice on Monday. Love the blog and am happy to comply with your requests.

JewelyaZ said...

I went to bed, smug, thinking Kingston would get some snow but probably nobody else.

Just woke up to check on a noise, and discovered tbat Phantom Lake in Bellevue has 1.5" of snow down already with more falling.

I hope the kids have school!

Anonymous said...

We have an inch or so in Sammamish as well....4:46am.

Brian said...

Pretty good accumulation on Union Hill in Redmond (SURPRISE!). Woke up, about to get the kids to wake up for school, look outside, and I thought it was just really frosty. I open the door, and there was snow on everything, and a good amount too!

Very, very neat! And the kids only have a 2-hour late start. Which is fine by both them, and me! :)

Josh-B said...

Just got a email from a helicopter pilot friend down under. Says he's never seen anything like this. Funny thing is he said that about Southern California twice in 5 years. Global Warming? Fuels Management? To many people living in the forest?

Anonymous said...

Near Bellevue square mall; inch of so...

hmmmm ...time to return to taking weather advice from lesser types like Jim Foreman?

Phil said...

It's funny how the anonymous guys are always the ones with something to say that is not constructive. Do us all a favor and take it elsewhere.

Anonymous said...

Phil.... man you are thin skinned....it was more of a dig at Foreman than it was at Cliff... But I guess the underlying issue is...is weather so unpredictable that when its "iffy" don't fool yourself into thinking even Cliff can predict the weather.... I don't think that's a terrible insult, ...