Snowmageddon warnings in North America come from tropics more than Arctic stratosphere

First ever study of how North America’s four main weather regimes are affected by polar vortex strength

University of Reading


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The four US weather regimes (clockwise from top left): Pacific Trough, Arctic High, Alaskan Ridge, Arctic Low. Red indicates warmer conditions and blue colder conditions

Credit: Simon Lee

Winter weather patterns in North America are dictated by changes to the polar vortex winds high in the atmosphere, but the most significant cold snaps are more likely influenced by the tropics, scientists have found.

A team led by the University of Reading conducted the first ever study to identify how the four main winter weather patterns in North America behave depending on the strength of the stratospheric polar vortex. This is a ribbon of wind and low pressure that circles the Arctic at heights of 10-50km, trapping cold air inside.

It is already well established that the vortex wind strength influences weather in Europe and Asia, and the study revealed it also has a strong effect on three out of the four main winter weather patterns in North America, giving forecasters an additional tool to understand potentially high-impact weather during winter.

The study, published in Geophysical Research Letters, also revealed that, unlike in Europe, the most extreme cold snaps affecting the whole of North America are not most likely to occur after a weak vortex. Instead, the shape of the vortex and conditions in the tropics were identified as stronger influences of these conditions.

Simon Lee, atmospheric scientist at the University of Reading and lead author of the study, said: “Despite the most extreme cold snaps experienced in North America often being described as ‘polar vortex outbreaks’, our study suggests vortex strength should not be considered as a cause.

“We know that a weakened polar vortex allows cold air to flood out from the Arctic over Europe and Asia, but we found this is surprisingly not the case the other side of the Atlantic.

“In fact, our work suggests we should actually look south to conditions around the equator, rather than north to the Arctic, for the causes of these widespread freezing conditions in North America.

“Our results did reveal that the polar vortex strength provides useful information on the likelihood of most weather patterns over the US and Canada further in advance, including some potentially disruptive temperature changes or heavy rain. The more accurate information populations have about upcoming changes in weather, the better they can prepare.”

One of the clearest suggested effects of a strong vortex was a 10-15% likelihood of extremely cold conditions in western parts of North America, including Alaska, but milder conditions in central and eastern parts of the US.

Another weather pattern found to most often follow neutral or strong vortex wind speeds brings temperatures 5°C above normal and wetter weather in the eastern US.

The exception in the results was that the weather pattern associated with the highest chance of the most widespread extreme cold in North America, in which average temperatures in the central US are more than 5°C below normal, was not found to have a strong dependence on a weaker vortex, as it does in Europe.

They found widespread extreme cold is more common when an area of high pressure extends up to Alaska, and the polar vortex stretches down towards North America – pushing cold Arctic air southward in the lower atmosphere.

The scientists say the influence of the stratosphere on weather patterns, as well as how this interacts with long-term weather patterns in the tropics like El Niño, should be studied further and incorporated into forecasts to improve their accuracy.

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From EurekAlert!

92 thoughts on “Snowmageddon warnings in North America come from tropics more than Arctic stratosphere

  1. That article didn’t really give me much insight into how the climate works.

    It’s probably true that the coldest winters in the U.S. are when a high pressure system sits up around Alaska which has the consequence of directing cold arctic air down into the United States.

    I think the question is why does this high pressure system establish itself here.

    • re: “I think the question is why does this high pressure system establish itself here.”

      Let’s start with what’s known: ‘Descending air’ in the middle of a high pressure system.

    • As Joe Bastardi of Weatherbell Analytics– the Madden Julian Oscillation describes the process. It essential starts with Indian Ocean dipole moment and thunderstorms releasing enormous amounts of heat in the upper stratosphere forming the Artic Highs.
      Historical analogue information has been known for years to cause cold Winters. This December warmth is a prelude to a very cold Jan-March this year.
      As new subscriber to Weatherbell Analytics that is what Joe has suggested. If I’m wrong in that assessment and your out there Joe please correct my evaluation.

      • Totally agree. JB has provided a lucid explanation of how the winter season will evolve the way you stated… see the Saturday Weekly summary (free) at Weatherbell.com… excellent stuff. JB is ruthlessly honest about delusions on both sides of the climate debate, and is just as tough on himself when his predictions fail (and why they failed).

      • Joe has a wonderful ability to remember similar maps from the past, but a computer can bring up analog maps. What Joe also recalls is the motion in the map. A map of a ridge and a trough is a static thing. Joe remembers if the ridges and troughs were digging or lifting.

        Me? I make a wild guess and then sit back to see how wrong I can be.

        It has recently been interesting to watch how the cold built at the Pole and especially in Alaska and the Canadian Archipelago the moment the flow around the Pole became quasi-zonal.

        https://sunriseswansong.wordpress.com/2019/12/28/aectic-sea-ice-slack-tide/

  2. This justifies a return to my old hypothesis set out here:

    https://www.newclimatemodel.com/is-the-sun-driving-ozone-and-changing-the-climate/

    whereby jet stream waviness is a consequence of the interaction between a top down solar effect above the poles and a bottom up oceanic effect from the tropics.

    The result of more such waviness is increasing extreme episodes of both warm and cold but overall increased global cloudiness that eventually cools the whole climate system.

  3. The troposphere is the lowest layer of Earth’s atmosphere. The troposphere starts at Earth’s surface and goes up to a height of 7 to 20 km (4 to 12 miles, or 23,000 to 65,000 feet) above sea level. Most of the mass (about 75-80%) of the atmosphere is in the troposphere. Almost all weather occurs within this layer. link

    So, given that most of the atmosphere is below the polar vortex why would it have much influence on the weather?

    Is it possible that conditions in the troposphere influence the stratosphere and not vice versa?

    • Because the temperature of the lower stratosphere over the poles affects the height of the tropopause over the poles and thus alters the gradient of tropopause height between equator and poles.
      Changes in that gradient affect Jetstream behaviour and overall global cloudiness.

        • That relies on the quirky climate science definition of “atmosphere”. If you look at this years SWAN instrument paper you will see Earth hydrogen molecules extend 640,000 Km into space way past the moon. So you could say that it the atmosphere boundary.

          Probably stick to the name you are talking about which is the thermosphere, and leave the word atmosphere alone.

        • Krisna I am wondering if the weird high speed jet streams are a consequence of the sun being quite. The other question that comes to mind is did this happen before the LIA??

  4. Since North America is surrounded by copious amounts of warm water in the winter on its southern flank (Pacific off California, the Gulf of Mexico and the Atlantic south of Cape Hatteras), all you need to do is get the winds blowing in from the southwest, south or southeast to hit the arctic air coming in from the north and bingo, you can have Snowmaggadon.

    I’m not so sure many people living in North America don’t know this already. It happens once or twice a winter.

  5. Of course the weather is influenced by the tropics. That’s the weather-engine that drives all the other “parts”, all the way to the poles.

  6. “..our work suggests we should actually look south to conditions around the equator….for the causes of these widespread freezing conditions in North America.”
    What a crock! These people just think the tax paying public is dumb enough to fund their “research”…

    • I had a very frustrating conversation recently with a self-described climatologist and IPCC reviewer. I tried to explain why the climate models could never work but they wouldn’t listen. They just kept repeating that the models simply followed the rules of physics. So the answer to this issue is remarkably simple: just look at the climate models’ runs from just before these temperature patterns appeared and the models will (a) show the temperature patterns as just experienced, and (b) explain why they occurred.

      Either that, or the models really will never work.

  7. For understanding the movements of atmosphere, read Marcel Leroux ! His Mobile Polar Anticyclone explains why North America can be frozen, not an alledged “vortex”.

    • Leroux was referring to the tendency of northern high pressure regions in the troposphere to drift equatorward taking cold air with them.
      That is consistent with my hypothesis concerning changes in the gradient of tropopause height between equator and poles.
      You will note that changes in the stratospheric polar vortex (which contains descending adiabatically warming air that depresses the tropopause over the poles) can facilitate the equatorward drift.

      • “Leroux was referring to the tendency of northern high pressure regions in the troposphere to drift equatorward taking cold air with them.”

        I think that describes what we see. High Pressure systems drift around unless acted upon by an outside force. Sometimes high pressure systems practically stop over one location for a period of ttime..

      • The oceans have tremendous thermal inertia ……….having stored massive amounts of heat from solar energy of previously active periods of the sun…………..which is still coming out after the sun has morphed to being less active.

        This lag between the peak in heating of the oceans from the sun and when the oceans burping out that heat is exhausted is probably, at least a decade.

    • Indeed. The “Polar vortex weakening” supposedly “permitting cold air to escape the polar regions” cannot be based on factual observations. Synoptic analysis of satellite imagery shows cold air masses in the lower troposphere constantly move from the polar regions toward the tropics, regardless of the season.
      Using averages tends to obliterate the real working of circulation hence those “Azores anticyclone” types of so called action centers. Observing circulation at work is truly the first order of business for anyone.

    • The good part about the jet stream dip into the lower U.S. is it is bringing in tropical air off the Pacific ocean, not arctic air.

    • I’m in the loop that has dipped down through the Rockies. There is little wind but I woke to a few inches of white stuff this morning, just enough moisture being brought up from the south to be frozen out by the northern cold.

  8. European MSM making a lot if the lack of snow in Moscow, because, of course, climate jitters. That it all seems to have gone to Minnesota is not mentioned, of course.

  9. @Krishna Ghans: When I read “first ever study of”… is my feeling, it didn’t worth a study.
    @Lititude: “…something weather forecasters have known for decades”.

    Very true!!
    It again shows how peer review works for some particular group of climate scientists. Actual innovative research from true scientists will suffer a long delay and most of the time will be rejected; whereas silly and known ideas are getting published so quickly in renowned journals.

  10. I start with the fact that it comes from EurekAlert! and proceed to the fact that it is research conducted at the University of Reading, before concluding with this question. Are they just correlating weather outcomes with stratospheric conditions and assuming causation? If the same “study” is repeated with next year’s conditions, will it contradict what “we know”? Null hypothesis anyone?

      • Ok, substitute the next four decades for next year if you like, it doesn’t touch my point.

        Are they inferring causation from correlation, or aren’t they? The reason I ask is that they claim to “know” that polar vortex causes cold events in Europe, but “surprisingly” not in North America. No hypothesis about the physical mechanism involved or what should be different in the North American case. If there is a physical process that is responsible for the correlation they discovered, why would the process not be applicable everywhere at the same latitude?

        So that sounds a lot like the rooster crowed and then the sun came up, therefore sunrises are caused by rooster crowing (on the farm). Then we checked a place with no roosters, and “surprisingly”, the sun still came up. Apparently in those areas, song birds chattering are more responsible for sunrise. However, in a few cases we observed alarm clocks having a strong effect.

        • It is a matter of geography.
          Arctic high pressure regions with their associated cold air can easily slip eastwards and southwards across the continental land mass to the east of the Rockies but such regions forming west of the Rockies cannot easily propagate eastwards so they tend to move southwards and are easily dissipated by warm Pacific waters to the south. Water has a hugely greater heat capacity compared to air.
          As always, a knowledge of basic meteorology provides answers.

          • What part of that involves a mechanism that depends on the stratosphere? And is that their hypothesis, or just yours? Your explanation can be perfectly correct without their correlation being a reflection of any physical reality.

          • The temperature of the stratosphere above the poles influences tropopause height above the poles and thus the likelihood of equator ward surges of cold higher pressure air in the troposphere.

  11. “Waiting on the Polar Vortex” sounds like a song title.

    Those of us that live in the real world have to prepare for sun, wind, rain, snow, and cold well in advance of any forecasts.
    When you have outside animals you best should fix the frost-free faucet and the heater on the water tank, and not wait until the researcher models claim it might get cold.
    Same with firewood, snow tires, and a warm coat. October, in the NH, is a good time to get these things done.

  12. Another stupid question: does the position of the magnetic pole have any affect on regional temperatures at all?

    • It will be on around 8th Jan in central US, an elongated High from Canada to the gulf coast with deep cold in the NE pulled down to the GOM.

  13. I found this article on the sun’s effect on the Jet Stream very interesting. I would be interested in thoughts on this.

    “Meridional Jet Stream” Upsets Europe’s Apple –and Pear– Cart
    http://bit.ly/2ZVxp2B

    August 8, 2019
    Europe is forecasting a sharp reduction to its apple and pear crop this season after a long-lasting spell of Spring cold followed by a brief (but much-documented) burst of July heat dealt production regions something of a one-two punch — yet another example of the Swings between Extremes brought on by a wavy jet stream, which itself is associated with historically low solar activity.
    …Furthermore, some regions of the planet actually warm during times of global cooling — the Arctic, Alaska and N Atlantic/S Greenland to name a few (though ‘warm’ to the Arctic, for example, still averages well-below zero, there is no additional melt):
    Temp change between 1780 (a year of normal solar activity) and 1680 (a year within the depths of the Maunder Minimum) — NASA
    Earth’s climate is cyclic, never linear — driven by the sun.
    And history is repeating, our star is again shutting down (relatively).

  14. The 2 MSM companies that control 80% of news publications in New Zealand are making big over a warm marine blob centered ~ 2000 km off our east coast. They then go on about tropical fish having been observed further Sth than ever and publish comments from the most extreme alarmist scientist in NZ. They make no mention of the cold trend surrounding the country.

    https://www.ospo.noaa.gov/data/sst/anomaly/2019/anomnight.12.26.2019.gif

    This cold zone has been creeping north and intensifying over the last month. Balanced journalism would surely discuss both phenomenon. The US and Australia have media that balance the debate, but NZ has none. We are now subjected to daily sermons with no means of reply.

    M

  15. Snowmageddon again? Yeah, we had that last winter and this time, deep cold and snowy winter is keeping itself out of my AO. And it can stay out! I don’t want to shovel snow this winter!!

  16. Ozone is a good tracer, as it defines the boundaries of cold air parcels like the polar vortex, an ironically good use for a trace gas 50-200X less concentrated than CO2; but it’s not a good basis for a climate theory, nor is the thermosphere, neither control the ocean temperature or the tropics.

    “An interesting feature of stratospheric circulation is the QBO in the tropical latitudes, which is driven by gravity waves that are convectively generated in the troposphere. The QBO induces a secondary circulation that is important for the global stratospheric transport of tracers, such as ozone[11] or water vapor. ”

    https://en.wikipedia.org/wiki/Stratosphere, and reference [11]

    “About 90 percent of the ozone in the atmosphere is contained in the stratosphere. Ozone concentrations are greatest between about 20 and 40 kilometres (66,000 and 131,000 ft), where they range from about 2 to 8 parts per million. If all of the ozone were compressed to the pressure of the air at sea level, it would be only 3 millimetres (1⁄8 inch) thick.[6]”

    https://en.wikipedia.org/wiki/Ozone_layer

    • but it’s not a good basis for a climate theory, nor is the thermosphere, neither control the ocean temperature or the tropics.

      Agree.

  17. It is the sun, lack of sunspots creates a a lack of magnetic pull, this upsets the polar vortex and jet stream and thus we have weather issues. How do we not all see this. It is so obvious.

  18. In the seventies and eighties, the Netherlands had cold snaps almost each year, you could always ice skating on the canals. There where only a few in the nineteens, ice skating on canals is becoming very rare. The EU will use climate change to destroy democratie and soeverainity. Our only chance is the return of very cold winters that destroys their narrative, but i do not see happened and the msm will not mention the cold in usa.

  19. Question from a non-meteorologist:

    I think it is backward to speak of the “polar vortex “ as the active agent of high latitude weather systems.

    It would seem that the distribution and intensity of high and low pressure zones determines areas that are relatively warmer or cooler

    The vortex winds are a response to the natural rotation of atmospheric flow around these high/low pressure zones. Stronger vortex winds reflect greater pressure differentials, and vice-versa for weaker winds

    Am I on the right track here? If not, I am more than happy to be educated

    • Jim, there are two schools: the altitude one that seems to prevail these days, claiming everything comes from jet stream and other stratospheric little dense air… And the lower troposphere school where denser air masses do control what’s happening in lesser dense altitude.
      Marcel Leroux in his key paper https://hacenearezkifr.files.wordpress.com/2018/05/leroux-1993c.pdf
      explains what he has observed and measured.
      Instead of nullschool.net especially at 500 hPa, read the Leroux paper and then take the time to go to https://www.goes.noaa.gov/dimg/jma/fd/ir4/10.gif
      and observe how MPH are evolving over a year. You’ll quickly realize that polar air masses at all seasons tend to reach the tropics and are in no way limited by THE jet stream…

      • re: ” there are two schools: the altitude one that seems to prevail these days, claiming everything comes from jet stream and other stratospheric little dense air… And the lower troposphere school where denser air masses do control what’s happening in lesser dense altitude.”

        It does seem that most ppl “latch onto” the jet stream as some sort of controlling mechanism, whereas the material I was brought up on showed the jet to be a creature (created indirectly) of (by) interacting high and low pressure systems and their interacting fronts.

        • Leroux’s take is that the jets are a consequence of the lower tropospheric circulation. And it makes way more sense to me, especially because satellite observation of lower layers circulation does explain the appearance of the jets their development and then their demise. That’s why calling them THE jet stream is abusive by any means.
          I personally like this website to monitor the jets. And it does animations to better visualize their evolution. http://squall.sfsu.edu/crws/jetstream.html

          • For over two decades now (gosh, has been that long now?) I’ve been making use of these folks ‘weather data’ http://weather.rap.ucar.edu and particularly, their satellite imagery webpage: http://weather.rap.ucar.edu/satellite/ and http://weather.rap.ucar.edu/upper/ (upper winds).

            Observing for “divergence” in upper level wind patterns has been ‘the clue’ for up-coming severe weather outbreaks, in combination with the necessary moisture (water vapor) in the lower levels.

            I think today’s “over reliance” of spotting ‘the jet’ is a product of easily created graphics that the human mind THEN places value on, whether or not that value is ‘true value’, giving the observer that warm-fuzzy feeling one gets from confidence. In reality, its a “foolie”, a step or two away from the actuality of the atmospheric physics/the dynamics of ‘fluid flow’ actually taking place. I’ve raised this point a time or two in the past, and the comment always has been ignored. I’ll take a look at Leroux’s material too, now.

    • IMO, you’re on the right track Jim. Over the pole the stratosphere has much more mass and molecules than over the equator. This is simply because the tropopause is at ~28,000 ft (defined by the convective humidity level that can get up to about that height and no higher over the pole).

      So all above that humidity altitude level is deemed to be in the low humidity ‘stratosphere’. But the stratosphere-proper is defined by its temperature inversion which at present, over the Antarctic is at ~42,000 feet, where the temperature begins to rise again above that. That is where the polar stratosphere really begins, as the air below that T inversion is effectively just like the troposphere with less vertical motion. But there is in fact vertical motion, it’s just more organised within sinking and rising air in weak Lows and persistent weak Highs.

      So from 28,000 ft to about 42,000 feet the air keeps cooling with increasing height, just like the troposphere below that alt range does. The only difference between this lower most stratosphere and troposphere under it is, (1) it’s ~1% humidity, (2) it’s even colder than the tropopause below.

      Other than that potential pressure isobars and winds in the range 40,000 ft to 28,000 ft show that the lower most stratosphere readily sinks into the tropopause. In fact Highs at 39,000 ft do sink all the way from there to the high altitude icesheet just 15,000 ft below the tropopause. The Highs tend to sink in cohesive columns from just below the inversion level, all the way to the icesheet due to less convection disruption. As they do so they dump colder air into the polar- and mid-latitude Hadley Cells, cooling them.

      IMO, if that sinking cooling air increases in rate, via whatever stratospheric relative cooling process near to or above the inversion, then the polar troposphere will NET cool down over several years and the growing coldness transported equatorward by the polar and then sub-tropical jetstream.

      Established and fairly stable pressure systems do dominate the lower-most troposphere’s slower more organised vertical and also lateral flows, but it’s disrupted and altered by transient waves.

      • The last paragraph should say:

        “Established and fairly stable pressure systems do dominate the lower-most STRATOSPHERE’S slower more organised vertical and also lateral flows …

  20. “The US and Australia have media that balance the debate, but NZ has none. We are now subjected to daily sermons with no means of reply.”

    Michael Carter, you ALREADY replied.

    Who doesn’t want to hear Must feel: if NZ won’t read NZ gets told another way.

    • re: “The US and Australia have media that balance the debate”

      Ha! That’s funny … coming back from “humour hour” (happy hour to some types) already?

  21. _Jim January 8, 2020 at 10:29 am

    re: “The US and Australia have media that balance the debate”

    Ha! That’s funny … coming back from “humour hour” (happy hour to some types) already?
    ____________________________________

    Michael Carter December 28, 2019 at 11:46 am

    The 2 MSM companies that control 80% of news publications in New Zealand are making big over a warm marine blob centered ~ 2000 km off our east coast. They then go on about tropical fish having been observed further Sth than ever and publish comments from the most extreme alarmist scientist in NZ. They make no mention of the cold trend surrounding the country.

    https://www.ospo.noaa.gov/data/sst/anomaly/2019/anomnight.12.26.2019.gif

    This cold zone has been creeping north and intensifying over the last month. Balanced journalism would surely discuss both phenomenon.

    The US and Australia have media that balance the debate,

    but NZ has none. We are now subjected to daily sermons with no means of reply.

    M

    ____________________________________

    _Jim, wrong answer. Here’s not the post office of Michael Carter.

    What’s loose with you. That’s funny … coming back from “humour hour” (happy hour to some types) already?

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