Not the winter forecast

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  • Berries - no indicator of winter weather. Photo: David Davies/PA Wire

    Mince pies - already on the shelves. Photo: Yui Mok/Press Association Images

    The River Severn at Ironbridge, near Telford, Shropshire, on the mild Christmas Day of 2011. Photo: Nick Potts/PA Wire

    Eurasian snow cover on 31 October 2011 - below average extent. Image: NOAA, National Ice Center

  • Not the winter forecast
    20.09.2012 15:35

     

    A colleague brought mince pies into the MeteoGroup office this week. Mince pies. In September.

    Delicious though they may be, this seems a trifle early. And the manufacturer made no bones about the seasonality of the sweetmeats, plastering “Christmas” labels and motifs across the box.

    Once summer is over there is little to stem the accelerating stream of seasonal produce, even given that Hallowe’en and Guy Fawkes Night get in the way. And it seems to become more noticeable as we see the number of morning frosts increasing.

    It has been cold enough for a ground frost in a few places this week – certainly in parts of inland Scotland but also even in some rural parts of southern England, in well known frost-hollows such as Chesham in Buckinghamshire.

    On Saturday morning rather more places may have a ground frost, and parts of Scotland and northern England an air frost with temperatures here just dipping below zero.

    This, along with a sprinkling of snow on the Cairngorms, has led some eager individuals to speculate about the prospects for winter. Does this already indicate that we are in for a severe winter and a white Christmas?

    Well, of course there is no indication one way or the other, and there is no significance in a touch of ground frost and a dusting of snow on mountains tops in September.

    Every year we also hear the old adages about bird migration and berries. If we see certain of our avian friends arriving or leaving early it is sometimes concluded that “they must know something”. And when there is a profusion of berries in autumn it is often postulated that this is because nature is stocking its larder for a cold and snowy winter ahead.

    Unfortunately we heard this last autumn: there were boughs heaving with bright red berries leading to all sorts of dire predictions about feet of snow but the greater part of winter was not cold or snowy in the slightest, until that frigid outbreak in February.

    Birds and berries react to past and present conditions and are unreliable forecasters. It is possible that the atmospheric patterns that bring about a flourishing of berries might slightly more often than not be followed by one that produces cold or snow but there is no confirmation of that.

    Although there are cavalier assumptions that it is possible to forecast a season ahead, regular failures in that regard show how difficult it is for both amateurs and professionals alike. 

    Winter weather will be predicated on a number of atmospheric and oceanic drivers, some of them conflicting, and it is far too early to attempt a prognostication given this complexity.

    There is one indicator that does have some success but we will have to wait until the second half of October to see how that is evolving. It is the advancement – or not – of snow cover across Eurasia. If this is rapid there is some evidence that shows that Europe is more susceptible to experiencing extreme cold outbreaks brought on north-easterly winds.

    So we will have to wait until close to Hallowe’en to be able even begin to guess at what winter might bring. The only inevitability is that preparations for Christmas will by then be in full swing.

    By: Stephen Davenport