Santa’s snow forecast for Christmas 2012

With children all over Scotland eagerly anticipating the imminent arrival of Santa, they will surely be wondering whether there’ll be enough snow for him to arrive by sledge this year. So, the University of the Highlands and Islands news team have joined up with meteorologist Dr Eddy Graham, to help determine the odds of a White Christmas occurring this year!

Why is there such an interest in snow at Christmas?

The idea of snow at Christmas is very much deep-seated and etched into our culture - we seem to yearn for the beautiful snow scenes depicted on our Christmas cards each year, as though Christmas could not be perfect without a covering of snow upon the landscape. Yet, the stark reality borne out by the climatological statistics is that snow is a rather unlikely occurrence in Scotland at Christmas time, at least on low ground near the main centres of population (see Table 1 below).

The interest in snow at Christmas appears to originate from during the colder climate of the “Little Ice Age”, between about 1550 and 1850 A.D., when the climate of Europe was half of a degree Celsius colder than today, and winters were particularly prolonged and severe. However, the changeover from the Julian to the Gregorian calendar in 1752 made Christmas arrive 12 days earlier in the year, meaning the likelihood of snow was somewhat diminished thereafter. Later, the writings of Dickens in the 19^th century (e.g. “A Christmas Carol”) promoted the idea that Christmas was always a cold, frosty and snowy time.

What about global warming? Is it having an impact on the frequency of White Christmases?

There is no doubt that, overall, winters are getting milder in Scotland. For example, average air temperatures have risen by about +0.5degC since the mid-1970s, and the number of frost days across the islands and in coastal regions has decreased by more than a third (from 40 to 25 days per year) over the same time. The persistence of snow on many of the Scottish mountains has also decreased in recent decades. The Decembers of the past ten or twenty years, however, have seen a buck to this trend, and there has been a number of recent White Christmases, such as in 1993, 1995, 2004, 2009 and 2010 (who can forget 2010?). Some scientists have suggested that our recent cold Decembers are related to the loss of sea-ice in the Arctic Ocean, others say it is due to the inactivity of the Sun. However, a clustering of cold Decembers does not indicate a trend and it is far from certain yet whether this will continue or not.

And so what for 2012? Will Santa be needing a sledge or water skis this year?

November and the first half of December this year have brought colder than average conditions, though it has not been excessively cold, and the chilly weather has been punctuated by much milder and damper spells at times. The current meteorological prognoses for the week ahead (up to Christmas Day) indicate that Scotland will remain within the “battle-ground zone”, between very cold continental air lying just to the east of Scotland and much milder Atlantic air located to the south-west of Ireland, and there is currently no clear signal as to which airmass will eventually win the battle. Thus, both colder and warmer spells of weather are expected between now and the Christmas holiday period. Where the two air-masses meet each other in the form of weather fronts, heavy precipitation is likely at times, together with strong winds. Further significant snowfall is possible over the mountains, particularly in the north of the country.

Whatever the weather may be this Christmas, may you have a joyful and peaceful festive season!

Dr Eddy Graham

The probability of snow lying on Christmas morning at a selection of towns and cities across Scotland: