6 Feb 2014

The jet stream has a lot to answer for – and not just here in the UK

This winter in the UK has been characterised by perpetual storminess that has seen low pressure after low pressure arrive on our shores, bringing disruption and flooding that has continued since the end of December.

The cause of the stormy weather has been the jet stream – the fast-moving ribbon of air five miles up in the atmosphere – that drives the weather that we experience down here at the surface.

It’s been particularly powerful this year thanks to extremely cold air flooding off eastern Canada and colliding with sub-tropical tropical air, boosting it to speeds of 200-230mph.

zz_jetstream_wp

The jet stream doesn’t only play a big part in creating deep areas of low pressure, but also acts as an atmospheric superhighway – transporting them from one place to another.

With the jet stream being stuck in more or less the same position all winter, it has meant that we’ve been left with a stormy weather pattern for almost two months.

What drives the jet stream?

The jet stream is driven by the huge temperature contrast between the cold poles and warm equator and will often follow the zone where the greatest temperature difference occurs over the shortest distance.

This varies from season to season, with this zone often being north of the UK in late-spring and summer and close to or over the UK during autumn and winter – giving us our most unsettled spells of weather of the year.

As the temperature contrast has been especially strong this winter, the storms that have affected us have been frequent and intense.

Jet stream’s global influence

california_drought_g_wpWe are not the only part of the world to have weather that has been stuck in a rut this winter.

Across the Atlantic in the US, the jet stream has also been locked in the same position for much of the winter, having different effects on different parts of the country.

The jet stream has been taking a path northwards to the west of the US, before reaching into central Canada and diving southwards across the Midwest.

When the jet stream heads north, it takes warm air with it, as well as forming areas of high pressure. This has led to California suffering from a lack of rain and snow, with 90 per cent of the state in severe drought and 67 per cent extreme drought.

newyork_snowstreet_g_wpWhen the jet stream heads south, it takes cold air with it, as well as forming areas of low pressure. This has caused the eastern half of the US to experience its coldest weather in decades, as well as delivering lots of snow.

So, the jet stream being stuck in the same place for long periods of time this winter has brought extremes, albeit of a different nature, to different parts of the world.

In the meantime, you can get the latest UK forecast on the Channel 4 Weather website. I’ll also be posting regular updates on Twitter – @liamdutton

Tweets by @liamdutton

8 reader comments

  1. Lord Beaverbrook says:

    Any thoughts on the strength of the current solar cycle and the position and strength of the jet stream?

    1. SonjaS. says:

      My first thought exactly. Could the absence of Sun’s magnetic activity have influenced the ‘stuck pattern’ of the polar jet stream?

    2. jan lengyel says:

      High levels of man made Co2 emissions already present in the atmosphere and the continuing acceleration of global emissions is poised to create a catastrophic effect on world climate. The Jet Stream’s unusal ossillations is a clear warning sign that humanity needs t take urgent action to limit the consequences of an unstable climate.

  2. Colin MacDonald says:

    Hello Liam, the jet stream, interesting stuff, however I have a question. If the jet stream has such a critical impact on our weather, why isn’t it an integral part of every weather forecast? My understanding is that if it moves from one position or another, we get good or bad weather accordingly, is that right?

    I can imagine future weather reports on TV – “the jetstream is in the ideal position for some lovely warm, stable weather for the next week…etc” or the opposite of course.
    Just a thought, thank you. Colin MacDonald

    1. simon robinson says:

      yes i agree,i do wish they would show the position of the jet stream and also if they can predict any change of the position too.

  3. Sheldon Kusselson says:

    Here is a loop of Blended Total Precipitable Water that goes back to December 1 at:
    http://www.ospo.noaa.gov/Products/bTPW/TPW_Animation.html?fromDate=20131201&fromHour=0&endDate=20140207&endHour=12&product=EUROPE_TPW&interval=12hours
    Quite an active period with many periods seeing a disturbance on average every couple of days. And since January 1, I’ve counted at least 18 or 19 disturbances to go by the UK or close to them at: http://www.ospo.noaa.gov/Products/bTPW/TPW_Animation.html?fromDate=20140101&fromHour=0&endDate=20140207&endHour=12&product=EUROPE_TPW&interval=6hours . You are more than welcome to use these loops/images, but you may want to save because we don’t keep it on our web site for more than 3 or 4 months.
    Any questions, let me know.

    Sheldon Kusselson
    NOAA/NESDIS
    http://www.ospo.noaa.gov/Products/bTPW/Product_Animation.html

  4. robin says:

    The jet stream flows at around 35,000 ft – the cruising altitude of jet aircraft. Does – or how does – the pollution they add affect the jet stream? I am sure atmospheric carbon dioxide pollution is affecting weather conditions, but not sure how the atmosphere is affected at different altitudes. All the thousands of tone of carbon dioxide added every day by aircraft must, surely, have some effect?

    1. Meg Howarth/ @howarthm says:

      Good question – thanks. I’d like to know too.

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