NOAA
Positive versus negative Arctic Oscillation
As a former New Englander living in what should be a four-season region (and with due deference to Kent's S.A.D.), I expect winter to be beautiful, messy and miserably inconvenient. Because I expect it to snow in the winter. So far Central Park is showing goose eggs but the fine folks in the Pacific Northwest are getting clobbered.
What's up with that?
I know this post is going to spark a global warming discussion, but what I'm really interested in is the actual meteorological mechanism that's at work. As it happens, NASA has just published a succinct little explanation of what's guiding the weather so far this season. The short answer: Positive Arctic Oscillation and La Niña.
Arctic Oscillation (AO) has to do with the air moving around the North Pole. A positive AO is associated with low pressure over the North Pole, which keeps the cold air up at the higher latitudes. Negative AO is associated with higher pressure over the North Pole, so the cold air moves farther south and we in the northeast get those nose-hair freezing blasts from across Canada.
The NASA explanation shows us this graph of the pressure for this year's positive AO as compared with this graph of the pressure for last year's negative AO.
La Niña is about colder surface water temperatures in the Pacific, which is frankly hard to see here, but I'll take their word for it.
The NASA explanation says that it has the effect of "push(ing) the jet stream and the cold arctic air northward." But at the NOAA FAQ page I find some more specific information.
For example, this is a map of average temperature ranks during La Niña events from November to January. That does indeed look familiar.
NOAA
And here's the map of the average for precipitation for those same months.
NOAA
A recipe for snow in Seattle (and not in New York... yet).
(The deeper I dig on this, the more disagreement I find that these two conditions are necessarily predictive. I welcome any deeper insights you can share on the matter.)
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Precipitation depends upon jet streams that were discovered in the 1940s.
The average location of the jet streams in the northern hemisphere have been moving toward the pole at about 1 mile/year since their discovery. This is happening because our air has been heating up.
The jet stream at 30 degrees is where cold-dry air from high altitude sinks so deserts form. This describes places like the Sahara and the American Southwest.
The jet stream at 60 degrees is where warm-moist air rises to hight altitude so rain clouds form. This describes places Washington, Canada and Europe. Most rainfall over the US happens when this jet stream warps and bends to form storms.
Air rises at the equator and that makes rain forests.
Air sinks over both poles. Arctic and Antarctic precipitation happens when the jet stream at 60 degrees warps and bends - but both poles are otherwise arid.
Shifting average position of the jet stream means our air is transporting more heat to the poles every year. Solar heating has declined since 1700, and less energy has been coming from the sun. Jet stream movement is the result of air masses that expand as they are being heated, and this heating is due to carbon dioxide accumulation in the atmosphere.
Here is the important question - what happens if extra heat drives the northern-most jet stream all the way to the pole?
Answer - over 100 inches of ice accumulation every year over Canada and Northern Europe.
One foot of unmelted snowfall over the pole every week during fall, winter and spring.
This kind of perpetual ice storm would freeze animals inside a glacier while they have undigested vegitation in their stomach. Just like fossils found in the Arctic.
Entire cities could be buried under an ice sheet during a single storm if this kind of thing happens.
The northern jet stream hovers between northern California and southern Alaska in the west, but the Rocky Mountains pull the jet stream south over the Great Planes states.
A large El Nino corresponds with a large hot pool of water over the equatorial pacific. El Nino drives heavy rain around the equator that creates killer floods in South America. This drives the jet stream north, so the US gets drier while Canada gets wetter.
La Nina happens when equatorial water cools. This cools the air in the northern hemisphere and pulls the jet streams further south. La Nina causes drought in South America at the same time the US gets floods when rainfall that normally hits Canada falls mainly over the US.
The equatorial water cycles between El Nino and La Nina about every 3 to 10 years.
Air over the Arctic precess like a spinning top. This causes air to "wobble" with a period of 1 to 2 weeks. This is the Arctic Oscillation, and that bumps up against the jet stream, which move the jet stream north and south. That movement creates a phenomenon called a "cutoff low", also known as a storm, when spinning fingers of the jet stream are "pinched off".
The Arctic Oscillation goes through positive and negative phases, when the precession is stronger or weaker (more and less wobbling).
Negative cycles of the Arctic Oscillation combine with El Nino to cause prolonged periods of drought.
Positive cycles of the Arctic Oscillation combine with La Nina to cause floods and blizzards.
There are at least 5 other major climate cycles. Some are as long as several hundred years. The most well known is the ice age cycle that is about 110,000 years.
Good post Will. Thanks.
Yowsa, Crackhead. What you said - in the most succinct terms. I live in central Idaho and am so enjoying the La Nina end of this. :) But we have figured for years if it's the lady, look out. If it's the gentleman, a gentle winter is in store. And I wish more people would go to a paleomap and study the historical events of climate change, not the 40,000 year old ones. Rachel, I did it! I started the climate change debate! :)
if you believe in global warming you'll believe in anything
Climate has been a hobby since about 1980.
C02 isn't causing global warming like what people think.
Ocean water hold about 100,000 times more heat than air, so air temperature is not going to change until after ocean temperature changes.
Big shock. The ocean is heating up, but the air is not.
This is the first time ships have been able to pass over the pole from the Atlantic to the Pacific without an ice breaker since before the last ice age.
Tidal forces want to drive the ocean westward around the equator, but the Americas get in the way. That causes the Gulf Stream to funnel equatorial heat into the North Atlantic. That hot water melts ice that is not being completely replaced every year.
Arctic ice draws air downward, which cuts off most of the rain that would cause more ice to accumulate, so the ice that is being melted by the Gulf Stream is not being replaced.
That heat has been dissipated by ice since the end of the last ice age.
The Arctic is going to heat up when the ice is gone.
Hot water is where storms come from. Big storms.
Also.
The Panama strip in Central America was created about 4,000,000 years ago.
The Atlantic Ocean flowed into the Pacific through the Caribbean before that.
There were no ice ages until the Panama gap closed.
"That heat has been dissipated by ice since the end of the last ice age."
Does that really matter, as long as heat from sunlight is trapped on the Earth? The trapped heat is the same unless the heat is lost to space? Doesn't it eventually work itself out? Once you loose ice, doesn't the ground absorb more heat? That is of course if more heat is trapped on the Earth.
Will,
Thanks for the information. I live outside of Seatttle in the foothills and I sent in a pic of an ice covered tree in my yard. The snowwasa problem but the ice storm that followed the snow is really knocking out power in many areas.
I was raised in Ohio and this snow storm would not have caused anyone to blink. However because these events are not that common we don't have that many plows to deal with it. Also it is quite hilly in these parts.
I missed the show last night as I lost power and couldn't get my generator running. There is nothing like repairing a carburetor using a headlamp while laying in the snow.
As far as the big picture I don't really think we can say much to tie this event to global warming. Now if you look at all the weather events that hit the Red States last year you may have real cause to think that they are not as clued into what God thinks as Rick Santorum would have you beleive :)
The snow is going to get worse.
Crackhead,
I don't know where you get your information but every place I have checked for the last week has guessed wrong. I'll just hope you are too. :)
I'm getting my information from here:
This is called the National Oceanic and Atmospheric Administration.
They do weather monitoring and climate prediction.
I don't think I'm wrong. Follow the link.
We were looking at different time scales. I was talking about whether to go buy another 5 gallons of gas to get through the current power outage.
A far as long term forecasts, why do you think I bought a generator to start with :)
We'd love to share our snow w/ you guys out on the East Coast....in fact, you can have all of it =P. Except what we need to skii in the mountains. But in the cities we don't need any. It has been rather amusing to watch though: we've had 3 car accidents outside of my apartment complex since yesterday (I live near a main street). Amusing in that no one has been hurt and people in the Pacific NW apparently forget you have to brake at further distances when there's ice on the road.
Same thing in California. Rainfall seems to suck the brain right out of peoples' heads.
Snow in the NW and rain in Ca.
The common failure point is not having enough practice.
I was raised in snow and learned to drive in it. My wife and I went to get some generator gas today and it took me few tries to get up our short steep driveway. I enjoyed playing around with it but my wife almost had kittens. She's a California girl.
"...but my wife almost had kittens."
Well, Pat, that is a new expression for me lol
Hi Pat P11111
Does your wife know about carrying blankets, sandbags, and shovels in the car/truck in the winter?
Crackhead,
If there is any chance of snow she doesn't drive. When the snow hits I am her driver. We usually only have a couple snow events per year. We live in a small city and and she worked for the maintenance department. During snow events they would arrange for the snow plow to plow our street and pick her up and take her to work.
Well now I reckon climate change versus weather is a topic for later. Global warming is affecting climate but the usual cast of characters still drive weather patterns.
As pointed out by a transplant from Minnesota-If we had Seattle hills those would be ski runs not roads. Everyone seems to forget that despite low over all elevation Seattle and surrounding areas are far from flat. You drop a 175 vertical foot gain in 12 blocks into downtown Fargo and see who knows how to drive!
Thanks for the nice graphics, showing the problem with this year’s winter. As we gather more information from many unique perspectives over many years, we sometimes see exceptionally good graphics. It seems that good graphics and good explanations help understanding. Keeping Google Earth with the weather layer on stimulates the everyday understanding. As you glance at it daily and happen to have heard about some weather event sometimes a light switches on and you understand better, or more easily. It encourages the graphics or artist minded to consider better and more attractive graphics to depict global circulation in variety of forms. I am suggesting that since we have better data, and much better understanding such as this depiction (http: //upload.wikimedia.org /wikipedia/commons /6/6d/Earth_Global_Circulation.jpg) that we can pursue the idea of making a better graphics. The day to day Google Earth does not look much like this fine depiction, and it looks different from yours.
The NOAA web site shows a series of somewhat dated format, not a lot of hard won improvements on computer animation for science, over so the many years. (I was in advanced science HS in 1968, and more or less won the prize for drawing a simulated weather map, for warm/cold front, the map was drawn from simulated data where I created data for 36 weather stations and filled in every field of an 80 column simulated teletype report format to produce kind of data transmitted from the weather bureau.) The isobar the fronts are easy for me to read but boggles average the mind.
The site (http: //en.wikipedia.org /wiki/Atmospheric_circulation) is but a small start of collection of these sorts of images, and there is an entire college degree in the offering to assemble the many valuable historical images published.
I (being me) see things entirely differently (if not overly complicated) most of the time and find another excellent series of graphics in (http: //en.wikipedia.org /wiki/Earth's_energy_budget). As as well as others that promise to show complex aspects simplified.
The Sun is very constant in its output (386 quad-giga-watts), and but when earth’s distance from the sun (closest in the winter tilting away) and (furthest in the summer tilting toward) the average 171 penta-watts varies by 7%, these are geometric constants, that are reflected in what we call seasons where of the three effects the Earths tilt is the most significant for weather.
STOP here for moment I want to avoid talking about wind patterns and steering currents, mountain ranges, ocean and continental bodies because the wind is an effect and not a cause.
The Earth must rid itself of 23% of the sun’s energy that was absorbed by evaporating water. (The rest 77% is more or less automatic.)
So how does the Earth get rid of this huge amount of energy? The answer must be that the energy is absorbed by water in evaporating, and is released when that water vapor reverts to liquid water/snow. Now think about that, this is an equality, and it does not change without consequence, if it rains more on average the earth must get cooler it rains less on average the earth must get warmer. This too is a constant or a fact, but it not nearly that simple because of some opposing effects. Precipitation happens when the vapor condenses to liquid, but the Earth’s Atmosphere is non-condensing gas called air (o2, and n2), and air can absorb the heat given up by the precipitation as shown by an increase in temperature, an expansion of volume an becomes lighter and rises into those familiar billowing clouds. This is easily seen in summer by looking at a puffy cloud, turn in to a puppy, and then a rabbit, the sun provided the energy to evaporate the cloud, but the cloud bottom is cooled in the shadow making more cloud but heating the air that then rises releases the heat, the process repeats and repeats until we fall asleep.
This sun lit cloud heating happens by day, while cloud cooling happens more by night, this explains most of the vertical happenings, big system, and fronts also have a vertical component, heat, moisture, density and make up a very significant part of the weather cell.
The idea of a cell is good start; a graphical representation is quite difficult to see using the clouds shown in Google Earth. We see only light and dark areas, a series of broad streak having no scale, having a unmistakable hurricane/cyclone shape, and most without distinct boundaries all these things making the cell idea less attractive. Showing cell boundaries require some model to go by and lots of snap shot and clever calculations to become a good representation.
The interaction of the Hadley, Ferrel and polar cells are not static are it hard to assign them correctly, but a more significant look could track air masses and determine how they are born, grow, diminish and die.
I want to go back to energy, leaving chaos and witch craft behind. The majority of the energy comes to the earth in the Hadley cell regions, it’s the Earth’s shape that keeps the equator more directly in the hot sun. The moisture and heat add to the mass of the atmosphere and increase the height of the atmosphere over the equator’s Hadley cells. The altitude of the atmosphere over the Hadley cell is higher, and since the earth is spinning 1,000 miles per hour. As Hadley meets Ferrel the 1,000 mph high, sinks to the 700 mph Ferrel, the atmospheres momentum continues with a 300 mph jet stream.
Now we have wind, and because the cell boundaries move, and I could talk about wind patterns and steering currents, mountain ranges, oceans and continental bodies because the wind is an effect and not a cause.
The Earth loses much of the excess energy in the Ferrel cell, making the Hadley and Ferrel the most significant areas of loss.
The Earth tilts the North and South poles into total darkness six months of the years, perhaps moving the polar cells down ward and making winter all the worse. When Polar Regions are cold they stay cold, the energy from the tropics are not lost out a polar chimney.
If we understand that the Ferrel cell is the most important significant area of energy release, that the tropical regions hold very steady and that he polar cell do not help the earth loose excess heat then we can draw a better picture. (But I am not going to complaining about the lack of graphic tools.)
Good analysis.
Average ocean temperature doesn't change much because hotter sea temperature produces more clouds that block the sun.
Carbon dioxide adds a little more heat, but the overall effect is to make more clouds and more rain. Average annual rainfall in my county has increased from 17 inches to about 28 inches during my lifetime.
The thing that is changing in a big way is that Arctic ice is melting. The mysterious Northwest Passage that killed so many explorers is now open.
This is far better information than the earlier posts.
My question is... with all the rain Seattle gets, and the fact that it's in the NorthWest and MUST get cold in the Winter, why doesn't Seattle get MORE snow than it does? Honestly, I was shocked to find that the average snowfall amounts in Seattle are equal to that in North Texas! How can this be?
While you're right that we get cold in Seattle, our temps seem to hover between 35-39 for what seems like 6-8 straight weeks. We rarely "break through" that barrier that allows it to snow. Plus, another common misconception is that we get a ton of rain. While it does rain frequently, it is usually a minor drizzle, if much of anything. So even when it does get very cold, we get a dusting of snow. Storms like this one are extremely rare.
The ocean heats air over the pacific, including the Seattle area. Ocean water near Washington usually hovers around 50 degrees. Can't snow below 2,000 feet when steady western breezes prevail.
Air temperature drops about 1 degree for each 500 feet altitude. You need to be above 2,000 feet to get below 32 degrees most of the time.
The other thing that will cause snow is when a gigantic mass of frigid air slides south from the Arctic. That usually happens east of the Rocky mountains. Major sustained northern winds are required for several days over the north Pacific and Siberia to do this.
This sometimes brings snow as far south as Los Angeles. Very rare along the Pacific.
Coastal snow is usually limited to Canada and Alaska.
Thanks to all for the quick lesson in Seattle weather. I had no idea of the hills in Seattle either before having to drive there from across the country several years ago. They were quite a surprise. Must make for some fun sleigh riding when it does snow. :-)
Will this leave this summer just as hot in Texas as last year?
@Ralph, contrary to popular belief, Seattle doesn't get THAT much rainfall. Seattle's average rainfall is about 37 inches. That's the same as Dallas, Texas (37"), but less than New York City (around 47") and less than Atlanta, Georgia (about 50").
It's not that we get a ton of rain here in Seattle, I would say that it just 'spits' for days on end. It's the cloud cover that gets you, more than the actual rain. It's pretty rare for it to drop below freezing here. Our climate is fairly mild, not too cold in the winter but very rarely hot in the summer. This a range of 40-75 with little variation on either side. And since we deal with a snow event like this once maybe every few years we don't have the infrastructure to deal with. Don't forget our lovely hills either. ;)
All I know is, after this week Will, you can have your snow back.
On the plus side: this is a great time to convince your co-workers to a day of skiing up there in WA or down here in OR ;-)
As a Mainer, I honestly don't mind the snow. The worst part about this winter has been the up and down temperatures. We have days when the overnight low has been below zero, and the next day it's been close to forty.
Rumor is that my area is due for 3-6 inches of snow on Friday, but that amount of snow really amounts up to nothing in the grand scheme of things.
I seen snow once.I was a child and ran to the window declaring "look ma it's raining grits"
Then the Army sent my southern born southern bred behind to Germany! Now I know what snow is.
x
I would like to add, living in Eastern Washington now, and having been raised in Bremerton that we get plenty of snow over here every year because of those lovely mountains. They block our ocean air flow, darn it. I hate the snow for the most part, except on the rare occasions I actually get to go skiing, etc. Driving in it is terrible. Where I live I have almost 2 ft. of it and I dread it when the schools reopen next week trying to get my daughter to school. I would much rather deal in rain when it comes to driving.