UK Weather: How stormy has it been and why?

Since the start of December the UK has seen a prolonged period of particularly unsettled weather, with a series of storms tracking in off the Atlantic bringing strong winds and heavy rain.

The windiest month since 1993

In order to compare the recent spell with the numerous stormy periods of weather in the past the Met Office’s National Climate Information Centre has done an analysis of the number of weather stations in the UK which have registered winds over certain thresholds since the start of December.

This measure suggests that December 2013 is the stormiest December in records dating back to 1969 and is one of the windiest calendar months for the UK since January 1993.

December was also a very wet month across the UK, particularly in Scotland where it was the wettest December and wettest month overall in the records dating back to 1910.

But why has this been the case?

Storms are expected in winter

First of all, we do generally expect to see stormy conditions in winter months. This is because we see a particularly big difference in temperature between the cold air in the Arctic and the warm air in the tropics at this time of year.

This contrast in temperatures means we see a strong jet stream, which is a narrow band of fast moving winds high up in the atmosphere.

The jet stream can guide storms as they come across the Atlantic, and it has been sitting in the right place to bring those storms to the UK over the past few weeks.

There’s also a close link between the jet stream and storms. The jet stream can add to the strength of storms, but then storms can also increase the strength of the jet stream. This positive feedback means storms can often cluster together over a period of time.

But why has it been particularly stormy?

Even accounting for the fact that it’s winter, the jet stream has been particularly strong over the past few weeks – but why is this the case?

It’s partly due to particularly warm and cold air being squeezed together in the mid-latitudes, where the UK sits. This could be due to nothing more than the natural variability which governs Atlantic weather.

However, looking at the broader picture, there is one factor which could increase the risk of a stormy start to winter and this is called the quasi-biennial oscillation (QBO for short).

This is a cycle, discovered by the Met Office in 1959, which involves a narrow band of fast moving winds (much like our jet stream) which sits about 15 miles up over the equator. The cycle sees these winds flip from easterly to westerly roughly every 14 months.

In 1975 Met Office researchers discovered that when the QBO is in its westerly phase, it tends to increase the westerlies in our own jet stream – meaning there’s a higher risk of a stronger, more persistent jet stream with more vigorous Atlantic storms. It has been in its westerly phase since early 2013 and we expect it to decline over the next few months.

This is just one factor among many, however, which needs to be considered – so it doesn’t mean that the westerly phase of the QBO will always bring us stormy winters.

What about climate change?

Climate models provide a broad range of projections about changes in storm track and frequency of storms. While there’s currently no evidence to suggest that the UK is increasing in storminess, this is an active area of research under the national climate capability.

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43 Responses to UK Weather: How stormy has it been and why?

  1. Ian Dawson says:

    Unsurprisingly the Met office fails to mention that the increased temperature gradient is due to the greater than expected Arctic cooling(with commensurate expansion of its ice sheet).Acknowledging this of course goes against the grain of shrinkage/global warming scenarios!!!

  2. argylesock says:

    Reblogged this on Science on the Land and commented:
    argylesock says… Here’s our Met Office explaining the storms which have been battering our islands recently,

  3. Just a thought. Could a factor in the increased gradient also be due to a quiet Atlantic hurricane season leading to a build-up of warmth in the equatorial Atlantic thus increasing the heat available for transfer North? While this Westerly storm conveyor has been running, temperatures have been relatively warm – or so my CH heating oil gauge indicates. I’m perfectly happy to be shot down in flames over this BTW.

    • David Parker says:

      The temperatures of the tropics change far less than those of the poles relative to the average, so I suspect that the increased gradient resulting in the current storminess is mainly due to the extreme cold coming from the arctic to the NE of N. America.

  4. jsam says:

    Reblogged this on Gra Machree and commented:
    Swathes of North America are icy cold due to a polar vortex. Australia has had its warmest year ever. The globe has just experienced its warmest ever November. And it’s unpleasant in Blighty – deeply so.

    • John Benton says:

      Australia’s only had its “warmest year ever” because the data has been fudged through tampering (bit like New Zealand did a few years ago). Only upward changes to the measurements has resulted in this claim.

      • jsam says:

        I love a good conspiracy theory. I look forward to you providing a reputable source for your laughable smear.

        In the meantime, enjoy being the poster boy for conspiracy ideation. Stephan Lewandowsky is spot on.

      • jsam says:

        New Zealand? Remember, you lost your case against NIWA. And badly.

      • jbenton2013 says:

        Now you’re making things up. NIWA acknowledged their data was useless because of their unwarranted adjustments.

      • jsam says:

        You lost NIWA so badly the judge awarded costs against you.

        “The plaintiff does not succeed on any of its challenges to the three decisions of NIWA in issue. The application for judicial review is dismissed and judgment entered for the defendant. [and] The defendant is entitled to costs.”

  5. Bob Smith says:

    Jet stream again. Seems every few months a new weather event is explained as being prompted by something happening with the jetstream. A few years back I can’t remember the jet stream being mentioned at all.

    Is this new? has a run of such jetstream induced weather happened before, eg the 70s? or is this new? or is it my imagination?

    • scarecrow78 says:

      The Jest Stream has always been with us, it just seems forecasters on TV and elsewhere are more likely to mention it in their forecasts or when they are discussing a notable weather event.

      This is probably a change in the approach to public weather forecasting that has been happening since the early part of last decade.

  6. It seems that a sentence fragment from this post, ‘no evidence to suggest that the UK is increasing in storminess’, has been picked up by the climate change contrarian community and fed to the _Sun_.

    A ‘Sun Says’ editorial quotes Tim Farron MP and then David Cameron MP and says ‘The Met Office says: “There is currently no evidence that links our current storms to climate change.” ‘ I haven’t found a source for that quote, the nearest being here.

    Meanwhile, Sir David King said on BBC 5live: “storms and severe weather conditions that we might have expected to occur once in 100 years, say, in the past may now be happening more frequently. And the reason is – as predicted by scientists – that the climate is changing and as the climate changes we can anticipate quite a radical change in weather conditions.”

    Richard Allan, professor of climate science at Reading University also referred back to this page explaining “While individual storms or successions of storms cannot be linked directly to climate change, there are some aspects of a warming climate that are relatively well understood and have implications for the severity of impacts we suffer. As temperatures rise, basic physics dictates an increase in the amount of atmospheric moisture, which is the fuel for heavy rainfall events. That means whenever we have heavy (and prolonged) rainfall events in the future, we can expect them to be more intense – along with the risk of flooding.” (on

    So I wouldn’t want a statement from the Met Office to become a political football, but it might be good to add some clarification: for example, while attributing individual events is still very difficult, there is a likelihood of increased storms flooding in coming decades because of climate change. Or reiterate or link to past statements or Hadley Centre publications.

  7. jbenton2013 says:

    “no evidence ” means exactly that Cedric. It sounds like you’re not happy with that, and want some manufactured quickly before people catch on.

    • jsam says:

      Ah, good try at weasel words. But #denierfail.

      We need more data. I’m glad to see you want to see increased spending to provide the necessary data. The obvious hypothesis is that, with the undeniable increase in energy due to increased CO2, the weather will become more erratic. I know of no complex system that responds otherwise. So, let’s get the data, quickly, to demonstrate (or not) such).

      • Exactly. If someone is paid enough, they’ll find any data the donor wants to see. That’s warmist science in a nutshell, from the Hockey Stick to the present day.

      • jsam says:

        The hockey stick has been replicated, oh, a few dozen times now.

        If you don’t want to pay for the data you can play denier ostrich.

      • One of those replications was by using a bus timetable as the data input. Mann’s Hockey Stick has been demonstrated by reputable scientists as pure hokum of no value to the CAGW debate – apart from the dubious one of being a sacred relic of climastrology.

      • jsam says:

        Thanks to nutty deniers the hockey stick is now one of the most trusted graphs in science. Marcott, PAGES 2K. stalactites,stalagmites…

        Tsk, tsk. I do hope you’re contributing to Steyn’s; defence.

        “Having been investigated by almost one dozen bodies due to accusations of fraud, and none of those investigations having found Plaintiff’s [Mann’s] work to be fraudulent, it must be concluded that the accusations are provably false. Reference to Plaintiff, as a fraud is a misstatement of fact.”

        — DC Superior Court ruling Mann’s defamation suit against National Review and CEI, July 2013

        And this just in. Yum.

        There’s nought less sceptical than a “climate sceptic”.

    • “No evidence” of what, though? My question was whether the Sun had misrepresented the Met Office. It appears so, and any clarification (preferably from the Met Office or the Sun) would still be appreciated.

      By the way note that there is no contradiction between statements like “these weather events are within normal seasonal variability for period x-y”, and counterfactuals like “these storms would not have been as severe without QBO effects” or “these storms would not have been as severe without climate change”; nor unconditional assertions like “the QBO exists”, “QBO westerlies in general strengthen jet stream westerlies”, “climate change generally increases precipitation” or “storms are likely to increase in intensity in coming decades”.

      As to the other comments, not related to “storminess”, it seems to me reasonable for anyone describing themselves as a “sceptic” to ask for justification for claims. But that is only providing they have already made reasonable attempts to find and understand that justification, and also provide justification for any claims they make themselves. Or in other words, actually testing one’s own assertions against what is already known would be more widely seen as polite, worthwhile and sceptical.

  8. Many thanks for the response. I haven’t read the full report yet (stuck the wrong side of Dawlish!), but with luck that statement is clearer and less able to be misinterpreted, provided journalists can convey the difference between short and long-term patterns, and between weather predictions and climate predictions.

    The point that a long-term warming of the atmosphere means that short-term precipitation events become heavier on average does seem to getting through when meteorologists are interviewed, including today on Sky News, which also carried an interview with Lord Stern praising the Met Office. In my opinion, more research is very important to show how UK resources can be optimally spent on local adaptation to climate change.

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