Skip to content

Met Office & Sudden Stratospheric Warming

February 29, 2016

By Paul Homewood   




The Met Office has an interesting post on sudden stratospheric warming, sometimes referred to as the polar vortex:


Our atmospheric scientists are predicting a dramatic change in high altitude winds 50km above the ground and the imminent occurrence of an event known as a sudden stratospheric warming (SSW) in early March.

Professor Adam Scaife, Head of Monthly to Decadal Prediction explains: “Sudden stratospheric warming events occur high up in the atmosphere and involve a complete reversal of the high altitude polar jet stream – they can even affect weather at the surface, and for the UK a sudden stratospheric warming increases the risk of wintry weather.”

The phenomenon begins with a wave-like disturbance which travels up into the high-altitude jet stream. Scaife said: “This disturbance can grow to a point where it turns over and breaks, just like a wave on a beach.”

Normally the jet stream flows from west to east with some north and south oscillation, but the force from this high altitude disturbance pushes against the jet stream until the winds actually reverse and flow from east to west instead. Air then falls into the Arctic and is compressed so that it starts to warm: the temperature can rise by as much as 50C in just a few days.

Professor Scaife added: “This reversal of high altitude winds can also burrow down into the lower stratosphere. Once it is within reach of weather systems in the lower atmosphere the Atlantic jet stream often weakens and moves south. This allows cold air from the east into northern Europe and the UK.”

Sudden stratospheric warming events occur on average every couple of years and our long-range forecasts have consistently suggested an increased risk of sudden stratospheric warming towards the end of this winter. The last big event was in early 2013 and was followed by a cold end to winter. Although the impact of the current event is unlikely to be as severe, it increases the risk of cold north easterlies and wintry weather for the UK over the next few weeks.

Does this mean we’ll see snow at Easter?
You may have seen in the media that we will see snow at Easter. At this stage it is too early to provide details about what the weather will bring for Easter. Beyond a week ahead we can’t say what will happen on specific days, but we can give an idea of what type of weather we can expect.

As always we are working with our customers such as EasyJet and other major airlines, airports such as Heathrow and Gatwick, local councils, and energy providers, together with government partners in Highways England and Transport Scotland to ensure they are prepared for the current wintry conditions and whatever the weather may bring in the coming weeks.



  1. February 29, 2016 12:56 pm

    I’m surprised they haven’t given it a name: “Sudden Stratospheric Warming Shirley”?

  2. Randy Hall permalink
    February 29, 2016 2:29 pm

    Did you see this?

    Sent from my iPad > > >

  3. dearieme permalink
    February 29, 2016 2:47 pm

    It’s a fine old tradition that there’s always snow somewhere in the country after the start of the cricket season. Sometimes that somewhere is a cricket ground, especially in Derbyshire.

  4. John F. Hultquist permalink
    February 29, 2016 3:12 pm

    If the cold is 1,500 km away, do they get to record this as a win?

    Sort of like, “It is 5 o’clock somewhere.”

  5. David Richardson permalink
    February 29, 2016 4:47 pm

    I get it Paul – When the cold arrives (and it might or it might not) we have a ready made story. The Polar Vortex is generated by that extra molecule of CO2 in every 10,000 molecules of air. And its worse than we thought.

    Perhaps they subscribe to Piers Corbyn these days??

  6. February 29, 2016 5:50 pm

    That really has only just begun to bite then while it has yet to more than double by 2020.
    To say nothing of what it’s to cost the environmental luvvies.

  7. February 29, 2016 9:36 pm

    So, the Easterlies burrow down into the atmosphere and tickle the top of the weather systems in the Atlantic until they weaken them and this shifts the jet stream further south. This allows air in from the East into Northern Europe and the UK and greatly increases the risk of a cold snap and perhaps even snow.

    And this is another good reason why the UK should leave the common market.

    Guys, seriously, the reality is that when the AO index goes negative ( it indicates higher atmospheric pressure at the pole against a relatively stable atmospheric pressure in the mid latitudes, The vortex intensifies as cold air from the middle and upper stratosphere finds its way to the surface and flows southwards. It is vortex recovery after a warming event that brings the cold winds. There is a current warming that may peak shortly as you see here:
    This warming event represents a temporary invasion of the polar cap by ozone rich air from the periphery. Ozone levels increase as the winter progresses due to the paucity in short wave ionizing radiation and strong uplift of ozone rich air is endemic over the Pacific North American sector. Currently that zone of uplift is purging a mass of ozone rich air into the region of the upper vortex within the area of the polar cap producing a warming that is the due to the replacement of very cold air by warmer air…….no compression necessary.

    When the vortex recovers (cold air reoccupies the region of the polar cap) you may get your turn at experiencing the cold air from space that was experienced in the region of Lake Baikal back in the first half of January. But equally, it might flow southwards towards China. Perhaps, this time, since the zone of uplift is further East, more over the US than the north east Pacific Europe might experience the cold of Lake Baikal.

    Gordon Dobson observed back in 1920 that ozone maps surface pressure. Surface pressure and surface winds are a response to the distribution of ozone in the upper half of the atmospheric column, and more than the upper half in high latitudes. In fact ozone is ubiquitous in the atmosphere in high latitudes in both summer and winter. However, as surface pressure increases in winter a zone of descent of very cold mesospheric air establishes within the polar cap that finds its way down to about 250hPa. This air is cold, dense and virtually ozone free. It brings high surface pressure and outflows of cold air at the surface.

    It was projected by Shindel and other propagators of the AGW thesis that the Arctic Oscillation index would become progressively more positive under an enhanced CO2 regime. That would mean dominance of high latitudes by warm, moist air from the south rather than cold dry air from the north. I cant hear anyone saying: Sorry: I was wrong. Can you?

    But, ‘tickling the top of the weather systems’ is new. An original contribution from the land of Peter Rabbit.

  8. February 29, 2016 9:52 pm


    You see that low surface pressure at the pole (high AO index) is associated with warming of the air aloft. Warming = invasion of the polar cap region by ozone rich, low density air aloft = a sudden stratospheric warming.

    Conversely, as cold, ozone deficient, high density air from the mesosphere reasserts its presence over the polar cap, surface pressure will rise.

    The current ‘normal’ represents a ratio of the two types of air. That mesospheric air, and the air from the troposphere even more so, contains oxides of nitrogen hungry for ozone. The current normal is influential in determining the ozone content of the stratosphere. The distribution of ozone in the stratosphere determines the global circulation and surface weather. (And climate). Dobson was no fool. But he was followed by fools.

    • John F. Hultquist permalink
      February 29, 2016 10:50 pm

      Thanks erl.

  9. March 1, 2016 1:09 am

    You are welcome John,

    Just want to run through this again: High GPH in the lower part of the atmospheric column indicates lower density associated with the descent of ozone rich air. Negative values for GPH aloft indicates invasion of the upper air zone by cold mesospheric air. In winter surface pressure in the Arctic rises promoting the presence of that descending mesospheric air. In summer, pressure falls away and it disappears. A sudden stratospheric warming represents a premature substitution of the summer pattern.with ozone rich air dominating the profile, hence the fall in surface pressure.

    It follows that as pressure rises again with the reassertion of the presence of cold dense mesospheric air there will be an outflow of cold air from the high pressure regions associated with intense cold at the surface in those places that receive the air. The location of the highest pressure region is variable and so too the source of the air, and so also the destination of the cold air. In Europe very cold temperatures in Scandinavia are associated with high surface pressure. That should give a northerly component to the wind arriving at the UK.

    Re the warming in the lower column that coincides with outflows from the pole. What is relatively warm so far as the air in the lower atmospheric column is concerned is relatively very cold in those latitudes that are normally free of polar air flows.

    So we see the conjunction of warmer air at the surface over places like Greenland as East Asia freezes.

    The air in high latitudes is warmer than the surface during winter. So, it gets chilled as it moves across the surface.

    It adds up to a taste of the frigidity of space.

  10. March 1, 2016 1:59 am
    It is found that both the QBO [Quasi-biennial oscillation] and solar forcings in low latitudes can perturb the late winter polar vortex, likely via planetary wave divergence, causing an early breakdown of the vortex in the form of sudden stratospheric warming.

  11. March 1, 2016 5:10 am

    Kenneth. planetary waves that are basically just the polar front can not account for long term change in the polar atmosphere involving enhancement or loss of ozone concentration and long term change in surface pressure that is the direst consequence of change in ozone levels. In Antarctica we see a 10-15mb loss of surface pressure over the last 70 years.The loss of atmospheric mass has affected all latitudes south of 50° south.

    Planetary waves can not account for generalized ozone depletion in the southern hemisphere by comparison with the northern hemisphere.

    Ozone heating is the origin of so called ‘cold core’ polar cyclones that collectively create the polar front. These cyclones have a warm core aloft. You cant generate a cyclone without a warm core.

    So, the causation is the other way round. First ozone then polar front…that constitutes the planetary wave….a manifestation of the conjunction of mesospheric air inside the vortex with ozone rich air outside the vortex.

    It is the relative strength of the flow of mesospheric air, and perhaps its composition, into the winter polar stratosphere that governs ozone levels. It appears that uplift from the troposphere also plays a strong role.That uplift is generated by high latitudes and release of latent heat in low latitudes.

    All this is foreign to the world of IPCC climate science.

  12. April 8, 2016 1:44 am

    Reblogged this on Climate Collections.

Comments are closed.

%d bloggers like this: