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Stratospheric Phenomenon Is Bringing Frigid Cold to U.S

An unusual event playing out high in the atmosphere above the Arctic Circle is setting the stage for what could be weeks upon weeks of frigid cold across wide swaths of the U.S., having already helped to bring cold and snowy weather to parts of Europe.

Forecast high temperatures on Monday, Jan. 21, from the GFS computer model.
Click to enlarge the image. Credit: Weatherbell

This phenomenon, known as a “sudden stratospheric warming event,” started on Jan. 6, but is something that is just beginning to have an effect on weather patterns across North America and Europe. 

While the physics behind sudden stratospheric warming events are complicated, their implications are not: such events are often harbingers of colder weather in North America and Eurasia. The ongoing event favors colder and possibly stormier weather for as long as four to eight weeks after the event, meaning that after a mild start to the winter, the rest of this month and February could bring the coldest weather of the winter season to parts of the U.S., along with a heightened chance of snow.

Sudden stratospheric warming events take place in about half of all Northern Hemisphere winters, and they have been occurring with increasing frequency during the past decade, possibly related to the loss of Arctic sea ice due to global warming. Arctic sea ice declined to its smallest extent on record in September 2012.

An Arctic cold front was sliding south from Canada on Friday, getting ready to clear customs at the border on Saturday and Sunday, bringing an icy chill to areas from the Plains states through the Mid-Atlantic by early next week, including what promises to be a chilly second inauguration for President Obama. Temperatures in Washington on Monday are expected to hover in the low 30s, only a touch milder than Obama’s first inauguration, when the temperature was 28°F. 

Reinforcing shots of cold air are likely to affect the Upper Midwest, Great Plains and into the East throughout February, with some milder periods sandwiched in between.

Sudden stratospheric warming events occur when large atmospheric waves, known as Rossby waves, extend beyond the troposphere where most weather occurs, and into the stratosphere. This vertical transport of energy can set a complex process into motion that leads to the breakdown of the high altitude cold low pressure area that typically spins above the North Pole during the winter, which is known as the polar vortex.

The polar vortex plays a major role in determining how much Arctic air spills southward toward the mid-latitudes. When there is a strong polar vortex, cold air tends to stay bottled up in the Arctic. However, when the vortex weakens or is disrupted, like a spinning top that suddenly starts wobbling, it can cause polar air masses to surge south, while the Arctic experiences milder-than-average temperatures. 

During the ongoing stratospheric warming event, the polar vortex split in two, allowing polar air to spill out from the Arctic, as if a refrigerator door were suddenly opened.

An animation showing the evolution of the stratospheric warming event. The contours show absolute heights and the shading are height anomalies in the middle stratosphere, or about 16 miles above the surface. The height anomalies are a good proxy for temperature anomalies in the stratosphere with red representing high heights or warm temperatures and blue low heights or cold temperatures. You can see at the beginning of the loop a cohesive polar vortex along the coast of Northern Eurasia and then this area of higher heights or warm temperaturs rush poleward from Siberia into the polar vortex splitting it into two pieces, one over Eurasia and one over North America. The dramatic rise in heights or temperatures over the Pole is the sudden stratospheric warming. The result is that pieces of the polar vortex move equatorward and with it the associated cold temperatures. Usually something similar occurs in the troposphere in the ensuing weeks. Credit: AER/Justin Jones.

When the sudden stratospheric warming event began in early January, that signaled to weather forecasters that a cool down was more likely to occur by the end of the month, since it usually takes many days for developments in the stratosphere to affect weather in the troposphere, and vice versa.

“For reasons I don’t think we fully understand, the changes in the circulation that happen in the stratosphere [can] descend down all the way to the Earth’s surface,” said Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research (AER) in Massachusetts.

As the polar stratosphere warms, high pressure builds over the Arctic, causing the polar jet stream to weaken. At the same time, the midlatitude jet stream strengthens, while also becoming wavier, with deeper troughs and ridges corresponding to more intense storms and high pressure areas. In fact, sudden stratospheric warming events even make so-called “blocked” weather patterns more likely to occur, which tilts the odds in favor of the development of winter storms in the U.S. and Europe.

Cohen was the lead author of a 2009 study that found that sudden stratospheric warming events are becoming more frequent, a trend that may be related to an increase in fall snow cover across Eurasia. The increase in snow cover has in turn been tied to the rapid loss of Arctic sea ice, since the increase in open water in the fall means that there is more atmospheric moisture available to fall as rain or snow.

Cohen and his colleagues at AER have been using an index of Eurasian snow cover during the month of October in order to make seasonal weather forecasts for the following winter, and he said that by using this technique, they successfully predicted the ongoing stratospheric warming event 30-days in advance.

“As far as I know this is a first and has huge implications for intraseasonal predictions,” he said.

Computer model forecast for February, showing widespread cooler than average conditions in much of the U.S.
Click to enlarge the image. Credit: Weatherbell.

Cohen’s research has also pointed to stratospheric warming events as one of the reasons why the second half of recent winters in the Northern Hemisphere have turned out to be colder than the first half.

“Scientists about a decade ago predicted that stratospheric warmings would become less frequent with climate change, however, just the opposite has happened and they have become more frequent. There is a positive trend in stratospheric warmings since the turn of the century and I have argued this is contributing to more severe winters,” he said.

When the vortex becomes dislodged from the pole, Cohen said, it can lead to a flow of air that is more north to south than west to east. “So when the warm air rushes the pole it displaces the cold air over the pole and forces it equatorward,” Cohen said.

This has major implications for U.S. winter weather. 

High temperatures in North Dakota and Minnesota may not make it above zero Fahrenheit on Sunday and Monday. If Minneapolis records a high temperature below zero it will end its record-breaking streak of four years without such an occurrence. By Tuesday, the cold air will have spilled into Kentucky and Maryland as well as New England. And the long-range outlooks suggest that February is going to be a colder-than-average month from the Upper Midwest to the East Coast, although there may be brief breaks from the cold depending on the prevailing storm track.

Anthony Artusa, a seasonal climate forecaster at the National Oceanic and Atmospheric Administration (NOAA), said the cold air spilling southward for the inauguration may mark the beginning of a long-lasting cold period that is related to the stratospheric warming event. “It does look like this could be the early effects of it,” he said during a conference call with reporters on Thursday.

Related Content:
Winter Outlook Offers Hope For Skiers and Boarders
 Closer Look At Arctic Sea Ice Melt and Extreme Weather
isualizing 2012's Record Arctic Sea Ice Melt
arming Arctic May Be Causing Cooler Winters in Eastern U.S., Europe


By Joseph Marshall (Columbus, OH. 43214)
on January 18th, 2013

One of the things that perturbs me about popular press Winter severity articles like this is the high degree of ambiguity that surrounds words such as “colder”.  As a gardener, I use this term to refer to the maximum low winter temperature, since that is what determines perennial plant overwintering and is displayed in the USDA Zone Map.  But “colder” could also mean a lower average daily temperature with little to no change in the maximum low.  Or “colder” could mean a lower average daily low without affecting either the maximum low or the average daily temperature if the season is exceptionally clear and sunny.  Or it could even mean a lower average daily high temperature if the season is exceptionally cloudy with minimal change in the daily low temperature figures.  It could finally mean how consistent and stable these temperatures are over a given winter, as reflected in the clothes we are forced to wear and the gyrations we must go through to drive morning and evening.

Subjectively, for most of us a “colder winter” is experienced through how much trouble or discomfort we encounter driving back and forth from work.  We seldom experience either the daily low or high temperature except on weekends, which, in a given season could be warmer or colder on average.  We also, subjectively, experience “colder” as the severity of wind or snowfall or the relative frequency of either one.  This could be easily occur in a Winter with average temperatures close to the norm, but many days where temperatures fluctuate for long periods between 20 degrees F and 35 degrees F allowing unsettled weather patterns to persist.

All this is simply a recipe for a confused and misinformed public.  And more care should be taken to phrase these comparisons in clearer and better defined terms.


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By John E. Allen
on January 6th, 2014

The same can be said about what passes for stated daily highs and lows for the day.  Some weather reports state this as the daytime high and the night time low.  When the highs and lows occur at uncommon hours of the day, there seems to be no set way in which these kinds of occurrences are dealt with (displayed).  I prefer that the highs and lows are kept in the daytime, following nighttime format: that is temperatures recorded sun rise to following sunrise.  If they would simply state the hour in which the highs and lows occur, the information contained would be more accurate and useful.  The alternative is to stay within a Midnight to Midnight standard, utilizing the same tagging of the high and low hours of occurrence suggested above.  I would add the sunrise temp in all cases, as the general public finds this information the most useful of the day.

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By Andrew Freedman (New York)
on January 19th, 2013

Hi Joseph,

You’re right that the use of the word “colder” can have subjective interpretations. In this case, the colder air that is moving into the U.S. is simply much colder than any air mass so far this winter. Temperatures will go from being above average in the Plains, Midwest and East to below average for this time of year. For example, temperatures in the Dakotas may not get above 0°F for several days.

Will try to be more precise in language use from here on out.

Thanks for your comment.


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By handjive
on January 19th, 2013

That is some serious global warming.

Is there nothing carbon (sic) can’t do?

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By philbert (schaumburg, IL 60173)
on January 7th, 2014

O.K. I’m confused, I thought the carbondioxide was predominantly in the troposphere.  This article is blaming stratospheric heating so where’s the carbon effect?

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By AlexJ (Portland, OR)
on January 7th, 2014

As I understand it, the amplified greenhouse effect generally ‘cools’ the stratosphere because of increased infrared opacity through the atmospheric column. In this case, there’s a mechanism for “vertical” energy transport to the Arctic stratosphere, via Rossby waves.

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By Windy
on January 19th, 2013

@ “Scientists about a decade ago predicted that stratospheric warmings would become less frequent with climate change, however, just the opposite has happened and they have become more frequent.”

Many of the predicted events from a decade ago are falling by the wayside.

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By Martin Hanson (Auckland, New Zealand)
on January 19th, 2013

Frigid cold?

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By Ronald Berkley (Spring Branch, Texas 78070)
on January 20th, 2013

An article in Scientific America some years ago, perhaps 2004 or 2005, mentioned the North Atlantic Conveyor Belt could be affected by sea ice melting.  This very interesting article, “Stratospheric Phenomenon Is Bringing Frigid Cold to U.S” appears to parallel somewhat with the Scientific America’s article.  Melting sea ice mixed with slat water interferes with the polar jet stream causing Europe and North America to experience winters similar to Alaska and Siberia and the southern hemisphere would experience higher than normal temperatures.  If anyone could shed light on the Scientific America article and its title I would be most appreciative.  The technicalities are way above me but learning beats not knowing on any occation.

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By Ken (Sugar Creek, MO 64054)
on January 22nd, 2013

Hi Andrew,

With growing surprise and concern, the weather patterns of the last 20 years bring ever warmer overall trends.

One of these effects seems to be the “pumping” or added flow of warmer air masses into the Arctic. This then appears to deform the huge circumpolar “pancake” of cold air to where it will either veer southward as into Siberia and deliver a huge, colder winter there or lopping off a smaller section or sections to inundate North America or Europe causing locally acute cold waves. 

Yet the net of these effects continues to be more gradual global warming on the mega-scale.

One weather watcher describes it as a conveyor belt whose speed and polition as well as its aim are changing to where smaller but extreme cold air blasts invade North America, Europe or Siberia, much like a swing set will get destabilized the more energy is put into each push. In the extreme the system breaks down (or apart.)

So, it seems Hadley cells increase their reach and strength of flow causing hot conditions to flow northward and desert-like heat waves and droughts to affect us in the northern summer. Similarly, some cold blasts veer sothward. In spite of this the overall trend is warmer overnight lows, higher highs and a gradual rising of average temperatures.

What is expected for the end of winter / beginning of spring? I think we will see a considerable warming trend again. The Arctic winter ice extent is close to an historic low as of the third week of January and shows no sign of going the other way.

Does spring and summer look to be warmer again in spite of these wintry intrusions?

Thanks for an illuminating article.

Ken Wagner
Sugar Creek, Missouri

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By Tom Knapik (Carmel, IN 46033)
on July 20th, 2014

I write this as of 7/20/2014. Indianapolis Indiana. So far this summer has been cooler than average. It’s now July and we have has just experienced 23 days below average and we were within 1 degree of an all time low record temperature. The WX guy blamed it on a polar vortex.

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By Ryan Sarnataro (Santa Cruz)
on January 22nd, 2013

What I’m not seeing in these reports is speculation about how these events are essentially accelerating the warming of the arctic by moving vast amounts of cold air to the temperate zones for dissipation.  They seem to be another example of positive feedback.

If the arctic is looked at as a repository of thermal mass below the global mean temperature then these events are great equalizers.  If the reason there is significant polar ice the existence of a geographically excessive thermal gradient then the long term picture is even more pessimistic for the retention of any polar ice.

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By Penny Gray
on January 22nd, 2013

Wow, this is facinating.  Guess I’ll stoke up the wood stove.  What causes the onset of an ice age?  I realize we’re still coming out of the last ice age, but what causes these sudden shifts in global temperatures?

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By Stephanie Faulkner (Cleveland, NY)
on January 23rd, 2013

What I am also not seeing is any reference to the changing of the earth’s polarity that is also occurring now. For some reason this is not factored in and it should be.  Perhaps you could do another story on that and then tie the two together?  That Polar Wobble you talked about may have a direct correlation to that phenomena and in fact may be exacerbated by it.

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By David Thomson (Alma, IL 62807)
on January 23rd, 2013

The phrase “global warming” is a misnomer.  This presumes the ice in the Northern Hemisphere is the norm, when in fact, it is the anomaly.  Underneath the polar ice cap are extensive bogs, which indicate the normal long term climate involves a lack of ice.  What we are experiencing is “global thawing” and it has been occurring ever since the last ice advance over 10,000 years ago.

We are experiencing a transition phase as the climate attempts to return to old patterns. 

The overturning of the stratosphere in the Arctic should not be a surprise.  The atmosphere at northern and southern latitudes is considerably lower than at mid latitudes due to the inertial swing of the Earth’s rotation.

There are electric currents running through the ionosphere and Earth surface, which are also induced into mid elevations of the atmosphere.  These electric currents are carried by air molecules and consequently move the atmosphere.  These electric currents are affected by solar activity, Interstellar dust, and internal processes of the Earth.  The Sun is notably quieter this solar cycle due to an irregular transit of the solar barycenter relative to the Sun’s core.  As the Sun’s output decreases, so does its effect on the Earth’s electric currents.  In addition to the electric currents, the Earth’s overall electrostatic field is increasing.  The combination of all these factors affects the electric currents in our atmosphere and hence, our weather. 

These weather pattern changes have occurred over the life of the Earth and have nothing to do with human activity.

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By Reality Check (concord/ma/02835)
on January 23rd, 2013

I’ll not even attempt to pretend I know much about climatology.  However, I have been on this planet almost 60 years, and I can tell you there is no ‘normal’.  Geez, Here in Michigan we have in most winters experienced the ‘Arctic Express’.  January temps more often than not are in the single digits or less.  Also, some summers are hot and some are not.

Climate cannot be analyzed over a few decades.  You all may have your fancy degrees but you have no common sense.  The climate changes over eons of time and those changes have nothing to do with humans.  It has to do with the sun and it’s discharges, the tilt of the earth and many other things. 

Only oversized egos could believe we puny humans can affect the earth’s climate to any great degree.  These same oversized egos have a wonderful plan to trade carbon credits and get very rich off of them.

Wake up and investigate Al Gore for starters.  Mister McMansion himself burns more carbon heating his mansion and flying around the globe than the majority of us would expend in 40 years.  Hypocrites all.

I really don’t understand all the hysteria surrounding weather these days.  That the weather channel is now naming winter storms seems extreme, but then they can hype the storms looking for more viewers.  However, this is normal winter weather.  Wake up people.  You are all being duped for $$$.

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By Windy
on January 23rd, 2013

@ David Thomson

Are you the David Thompson researching the Aether physics model? Just curious, thanks.

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By Larry (Peoria,AZ)
on January 23rd, 2013

And nowhere in this article is a mention of the cyclone anomaly that has been “parked” over the North East Pacific approximately 200 miles west of British Columbia, sending these “waves” of cold fronts over the United States, presiding over the death of what is sure to be tons of produce in the most productive western states, including California’s central valley.

I am no meteorologist nor trained in weather phenomenon, I however have more than a passing interest in these events including solar system activity for many years now, and thereby believe that solar activity is more than intimately connected with what we experience in climate patterns here on earth as well as the rest of the solar system. And I am aware of the weather-altering effects of the ionospheric heating arrays in various locations.

I have been observing this “vortex” over the N.E. Pacific Ocean for more than a month now and never has it ever been mentioned in the media, nor the scientific journals as I see it sending wave after wave of low pressure systems into the U.S., including altering the path of the jet stream to divert southward. It is as plain as the craters on the moon and was easily observable through the GEOS satellite feeds.

Is there one knowledgeable person who can comment on this cyclonic anomaly…  it seems awfully man-made as it has literally not moved at all since I first noticed it about mid-December, 2012.

Re: Polar shift - I don’t think a polar shift has ever occurred due to observation of the Antarctic landmass below the ice shows it to have a toroidal-fractal pattern, thereby showing its location as an axis point has never changed during its formation.

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By Andrew
on January 23rd, 2013


The prevailing pattern has featured a high pressure area in the Northeast Pacific, and the circulation around it is helping to direct cold air into the Central and eastern U.S. This is most likely associated with the current phase of two natural climate cycles, known as the Pacific Decadal Oscillation, or PDO, and the Pacific North American Pattern, or PNA. I have not seen any research indicating whether and how these cycles are being influenced by climate change.


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By FishOutofWater (Jacksonville NC)
on January 24th, 2013

Ryan Hanrahan observed the polar night jet was slowing rapidly & the polar votex was beginning to split on January 4.

I picked up the story on the 15th.

The southward push of cold air had already helped intensify a storm in the west Pacific to exceptionally deep low pressure. The storm created huge waves that made it all the way across the Pacific to Half Moon Bay where they held the big wave surf contest at Mavericks.

I’m looking forward to research reports on this event.

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By Ed
on January 24th, 2013

Displaced polar vortex? Jet stream buckled? Are these “normal” attributes to N Hemi winter? Im just a WV loop junkie who is looking for answers…

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By Geoff Sharp
on January 26th, 2013

The SSW events are solar related and have nothing to do with Arctic ice or so called man made global warming in my opinion.

This year the QBO is favorable for planetary waves that are also assisted by the ozone changes at different levels that have been influenced by the very low UV levels experienced by what will be known as the Landscheidt Minimum. These planetary waves are what break up the northern (only) polar vortex.

This was predicted back in July.

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By ChristiRN (Haskell, OK 74436)
on January 28th, 2013

I live in Oklahoma and I was looking forward to this colder weather to maybe cut down on some bugs and see a little snow.  Unfortunately, we haven’t seen any.  It’s 65 degrees at 8 am today.

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By Dominic Scerbo (Trumbull)
on March 25th, 2013

I appreciate your post Andrew.

Question: any similar correlation of stratospheric temperature swings to resultant tropospheric temps during the summer months?  Would appreciate any input you can provide.


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By Dave Kuck (Sheboygan/WI/53083)
on March 28th, 2013


We have been on vacation in Florida for the entire month of March. Cold-30 mile per hour winds-58 degrees two days ago. We have not had one day in the 70’s except for the first day of our arrival. Gave up hoping the photons would help us out on sunny days:) If this is a possible new norm every other year or so-I will need to head further south.

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By Copie
on April 1st, 2013

Andrew Freedman, you must be desperate to come up with this ridiculous sudden stratospheric warming gimmick to try to justify your discredited theory. Even the UK Met office have now admitted that there has been no warming for the past 16 years. I am looking forward to the day when you, James Hansen, Michael Mann and Bill McKibben are charged with fraud for claiming that record cold weather is really global warming.

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