Weather

All change with first taste of winter possible next week

Forty-eight hours can be a long time in weather forecasting, and since I wrote my blog on Monday there’s been a growing trend for colder air to start influencing our weather from the near continent next week.

The award for the biggest flip-flop goes to the American GFS model which has performed an impressive volte-face in the last forty-eight hours.

As I’ve explained before, each model is run many times, with slightly different initial atmospheric conditions.

This allows forecasters to judge how likely a particular scenario is; in other words it gives us a level of confidence.

Currently, around sixty percent of the solutions from the European (ECMWF) model suggest that cold air from the east will win the battle against the milder Atlantic air that has been with us for virtually the whole of winter so far.

For other models the percentage of cold solutions is around fifty percent.

So at this stage although colder weather next week is more likely than not, it’s by no means a done deal and caution is required – particularly in light of the big jump from the GFS model since Monday.

In my twenty years as a forecaster I have seen many a cold easterly scenario turn into a figment of the computer’s imagination, with a flip-flop the other way to a milder scenario always a possibility.

That said, the European model is often the most reliable, and there has been a definite trend towards this colder scenario in the last few runs of computer models.

Whatever the final outcome, next week is likely to cause real headaches for forecasters, trying to determine just which air-mass will win, and where the battle between cold and mild air takes place.

Where that battle takes place, there will be a risk of some snow.

And let’s not forget, there will also be a risk of heavy rain, which could further exacerbate the flooding situation affecting parts of the UK.

So changes are afoot, but there’s still much uncertainty which could last for a few days yet.

Comments

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  • Comment number 43. Posted by greensand

    on 15 Jan 2014 23:58

    Happy New Year DW!

    "but it is falling more frequently as deluges"

    Well, whilst not my scene, but I do recognise you like to crunch the numbers you should find the following to be of interest. From what I can gather it is based on official Met Office data.

    "Corinne Le Quere Flooding Claims Rebuttal"

    "...So, I offer a very simple challenge to Corinne. Analyse the data back to 1910 and tell us all whether this still backs up your contention that “heavy precipitation in winter has increased”.

    If it does not, then your claim that climate change has increased the risk of flooding is no more than unscientific propaganda."

    http://notalotofpeopleknowthat.wordpress.com/2014/01/15/corinne-le-quere-flooding-claims-rebuttal/#more-6445

    PS. If you have issues with what is written in the article, take it up with the author. I have no interest, but as you obviously do I thought you might be interested.

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  • Comment number 42. Posted by newdwr54

    on 15 Jan 2014 23:10

    34. John Marshall

    No doubt there are land management issue with all floods. But according to the UK Climate Projections 2009 'Observed Trends Report', "all regions of the UK have experienced an increase over the past 45 years in the contribution to winter rainfall from heavy precipitation events": http://ukclimateprojections.metoffice.gov.uk/22647

    Overall winter rainfall hasn't increased much in the UK in 50 years, but it is falling more frequently as deluges and that can hardly be overlooked as a possible factor involved in increased flooding.

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  • Comment number 41. Posted by ashleyhr

    on 15 Jan 2014 23:03

    No ukip I would NOT. I was questioning the 'certainty' of climate change deniers such as yourself.

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  • Comment number 40. Posted by newdwr54

    on 15 Jan 2014 22:23

    35. Kelvdfv

    I don't know how accurate your thermometer is, but I'd like one of those!

    On clear days the lapse rate can be -6 deg C per km rise. You'd expect temp of -37 deg C at around 6km alt. if it's 2 deg C at the surface.

    Clouds trap outgoing heat in the atmosphere; radiating some of it back to the surface; so the temperature difference between the cloud base and the surface can be quite similar, depending on the alt. of the clouds and how dense they are.

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  • Comment number 39. Posted by JaimeJ

    on 15 Jan 2014 21:15

    Well Exacta Weather are now tweeting that it was just the unexpected increase in solar activity this winter which has 'delayed' the cold weather and snow. They still remain hopeful for a very cold late winter/early Spring! It would be far better IMO if they just admitted that they got it wrong and explained in a bit more detail why they think they got it wrong.

    It may indeed be the case that the Sun has been responsible in large measure for our very wet mild winter - so far. But we need a bit more in the way of evidence to convince us that this may be the case. Of course, I would demand the same of those who insist that CO2 has caused the recent flooding but I suspect the goods may not be forthcoming.

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  • Comment number 38. Posted by Ukip

    on 15 Jan 2014 20:58

    Ashleyhr. Interesting to see that 9 out of the 37 comments are yours. I call that Spam. If you was so confident of agw wouldn't you be sitting back and smiling to yourself, rather than trying to change other people's beliefs.

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  • Comment number 37. Posted by ashleyhr

    on 15 Jan 2014 18:27

    Kelvdfv
    You may wish to google 'lapse rates'. If I understand your question correctly.

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  • Comment number 36. Posted by ashleyhr

    on 15 Jan 2014 18:24

    Well the good news is that 'winter' 2013-14 in the UK is half over.

    I hope this may interest some here:
    http://www.bbc.co.uk/dna/mbpointsofview/NF1951566?thread=8446960&post=118428147#p118428147

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  • Comment number 35. Posted by Kelvdfv

    on 15 Jan 2014 14:24

    I got an infrared thermometer for Christmas. I have been measuring the sky temperature since then.
    On clear days when I point the thermometer directly above I have measured the sky as cold as minus 37°C with ground level air temperatures around 2°C. On cloudy days I have measured the cloud at 6°C, around the same as the ground level air temperature. Why is it that this big variation in temperature above doesn't seem to alter ground level air temperature very much?

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  • Comment number 34. Posted by John Marshall

    on 15 Jan 2014 12:24

    #30 nerdwr54

    As I posted, but you obviously did not read, river dredging is not carried out because of cost.

    Because of continual sedimentation flooding increases without dredging. I think that householders have a claim on central government for compensation for flooding imposed by government cutbacks to the EA and a claim against the EA for mismanagement of river maintenance causing floods.

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