Sunday, January 11, 2009

High Pressure and Air Pollution

The heavy rain is over and today and tomorrow we will transition to a week-long period of high pressure and dry conditions. Sounds like heaven? Well, there is a little detail we have to talk about...

Anyway, right now the pressure over us is already extraordinarily high....about 1040 mb (30.70 inches of mercury). In fact, it really is rare to get rain (as we are right now in some areas) with such high pressure.

All the computers models agree that we are about to transition to an extended period where high pressure will build along the West Coast....take a look at the attached figure for Tuesday at 4 PM--the figure shows the flow at 500 mb...about 18k feet aloft). Like sea level pressure better? The next figure shows that at the same time.

Such high pressure will bring absolutely dry conditions and MUCH warmer temperatures aloft. If this was late spring or summer, we could be looking forward to record-breaking temperatures...and some might cancel that trip to Hawaii. But before you do so, remember this is January in Seattle.
The problem this time of the year is that when high pressure builds over us during midwinter, we often develop low-level inversions and fog. Warming aloft is certain. But the sun is still weak and it can't heat up the ground much and there is good radiational cooling to space during the long nights. Fog can form at night and can become very persistent...and in fact it helps to maintain itself for reasons I won't get into now. So there is a danger we can fog in and stay cool at low levels. Such fog can mess up air travel...so fly out as late as possible in the day if you want some insurance.

Our big hope is that the high pressure will slip sufficiently east to give us offshore and downslope flow...which can mix up the lower atmosphere and destroy the inversion. This is what local meteorologists will be analyzing in great depth this week.

And there is another threat...air pollution. Inversions act to prevent mixing of air in the vertical and pollutants can be increasingly concentrated. My colleagues at the Puget Sound Clean Air Agency are already concerned enough to provide initial warnings. There might be burn bans later in the week...so keep that in mind before you fire up your fireplace or woodburning stove.

So we had snow and ice and then heavy rain and floods. Now we may have fog, murk, and air pollution. But there is one good thing about the latest plague...you will be able to escape it by going up: the conditions will be sunny and warm in the mountains. Last time this situation occurred it was in the 30s and lower 40s in Seattle and 60F at Paradise near Mt. Rainier.

27 comments:

Joseph Ratliff said...

Cliff, you said the following:

"...you don't want to know what will follow the air pollution. "

Yes, I do. :)

What are the possibilities? Anything out of the ordinary, or are we speaking of "stagnant air advisories" and the like?

Anonymous said...

I would like to know what is following the air pollution, too. :-)

Arctic air mass and more snow? A howling windstorm? Summer?

Scooter08 said...

A biased opinion here because I love the snow but my guess is an Arctic blast. Not always the case, but in past winters when it gets real warm and the developing weather pattern sets up, an Arctic blast has followed. Perhaps the high pressure moves west and allows the west coast to be susceptible to Artic cold. By the tone of Cliff's "voice" that is what is on my mind.

Scooter08 said...

Also, looking at the NWS prediction for the next month, they are calling for much below normal temps, apparently this week aside. :)

Anonymous said...

Thanks for the cliffhanger- I hope you intend to answer it.

Anonymous said...

I expect we are due a little pestilence next--not a weather event, however.

Cliff must have 'talked' up the weather gods, since all this snow, ice, rain, Pineapple Express, etc. has really put a focus on his book. I know I have my autographed copy!

emma kaye

Cliff Mass Weather Blog said...

If only the weather gods would listen to me..

Joseph Ratliff said...

Then what Cliff? If the weather gods listened to you...would we be stormy all year long? :)

Still waiting on the straight up answer to the question here...

Jeff said...

Any word on when KIRO may televise the winter storm special? There was mention late in the week it was going to be on this afternoon/evening. I love all the video and facts about recent storms. Mean while.... I'm reading Cliff's book with half an ear on the football game. Good weekend to spend indoors:)

Anonymous said...

The winter storm special is on KIRO tonight from 7-8.

Anonymous said...

The Climate Prediction Center (CPC) is calling for above normal temperatures and below normal precipitation...up to Jan 25....

climo man said...

The Climate Prediction Center also publishes every day a number of maps that are very useful (and often quite accurate) in detemining what the general world weather pattern will be up to 15 days out.It correctly predicted the pattern that caused the December snow event well ahead of time.Of particular value is a 500 MB map that is an ensemble of many the various weather models.For those who are wondering what the weather will be after next week, check it out.I hate to disappoint some people, but it looks pretty "blah": continued high pressure, although gradually weakening.It`s hinting a more seasonal zonal flow by the end of the month.But keep checking the maps, sometimes the models change radically in a very short period!

climo man said...

I made a mistake on my previous entry. It`s the NCEP (ensemble mean) not the CPC, that publishes the 500 MB charts! But the CPC also has very easy to understand discussions of all their short range (6-10/8-14 day) and long range (monthly and seasonal) outlooks.

Rich said...

A little air pollution won't hurt anyone. I grew up near Pittsburgh in the 50s and 60s...now that's air pollution. So buck up.

Forgetmenot said...

Foggy mist moved in around 3pm today in Port Townsend. Sounds like it's here to stay.

e-North-West Tree Stewards said...

Don't high winds develop when the low to high pressure gradient is extreme? As this unusual high pressure moves east, are we more likely to have a significant wind event, assuming the typical winter lows come rolling in from the gulf?

Cliff Mass Weather Blog said...
This comment has been removed by the author.
Anonymous said...

i watched your interview on kiro this evening. it was the only interesting part, since it ignored lewis county as usual.

Cliff Mass Weather Blog said...

no strong winds...not enough pressure gradient over us....typically there are light winds when the high pressure is directly over us...cliff

Ashley said...

I think I might know what is coming after the air pollution... raining frogs? Locust swarms? I'd believe just about anything at this juncture ;)

JewelyaZ said...

The fog is so thick here in East Bellevue that where I can usually see about 100 meters to the back property line using the outside light on the back deck, tonight I can only see the chairs about halfway across the deck, which are about four meters from the door. Outrageous!

I'm glad I'm not trying to get on an airplane any time soon. Seems like fog is one thing that reliably causes real trouble at Sea-Tac, and I bet Cliff's right, there's going to be a lot of it for the next few days.

OTOH, current pressure is 1024 and the temp at almost 2 am is a balmy 48.2F. Good sleeping weather!

Jeff said...

Hey Cliff, good presentation on the storm special last night on KIRO. Like Bob Rivers told you on KZOK, you do have a good radio/TV voice. And too, it was nice to put a scientist personality along with the your blogs we read everyday.

Anonymous said...

Great job on KIRO last night! I just happened to stumble upon the special. You and Rebecca Stevenson made a great TV duo.

Josh-B said...

When there is yin (calm benign weather) there will be yang (wind, rain, fun).

Anonymous said...

Cliff, you're a meteorologist, right?

You went into the field because you love the weather, right?

Then why do a lot of your posts (like this one) reflect that you don't like weather? Check it out:

"The heavy rain is over and today and tomorrow we will transition to a week-long period of high pressure and dry conditions. Sounds like heaven?"

"The problem this time of the year is that when high pressure builds over us during midwinter, we often develop low-level inversions and fog."

"Our big hope is that the high pressure will slip sufficiently east to give us offshore and downslope flow...which can mix up the lower atmosphere and destroy the inversion."

So no weather is Heaven? Inversions and fog are "problems"? You have a "big hope" of no weather happening?

Doesn't sound like you like weather to me. Some of us actually do, so please let us enjoy it. Thanks.

Anonymous said...

Cliff, you're a meteorologist, right?

You went into the field because you love the weather, right?

Then why do a lot of your posts (like this one) reflect that you don't like weather? Check it out:

"The heavy rain is over and today and tomorrow we will transition to a week-long period of high pressure and dry conditions. Sounds like heaven?"

"The problem this time of the year is that when high pressure builds over us during midwinter, we often develop low-level inversions and fog."

"Our big hope is that the high pressure will slip sufficiently east to give us offshore and downslope flow...which can mix up the lower atmosphere and destroy the inversion."

So no weather is Heaven? Inversions and fog are "problems"? You have a "big hope" of no weather happening?

Doesn't sound like you like weather to me. Some of us actually do, so please let us enjoy it. Thanks.

Anonymous said...

Oh and I forgot one:

"But there is one good thing about the latest plague...you will be able to escape it by going up: the conditions will be sunny and warm in the mountains."

Good thing...escape it by going to sunny and warm places???
Plague?????????
People, this guy does NOT like weather. Don't believe him when he says he does, it's so obvious he doesn't.