12 December 2013

Weather forecast for Christmas - a white Christmas?

After two severe storms – in late October and the December storm that paralysed the country and caused chaos on the road and the flooding of large areas, what do we have in store for Christmas? Will there be another severe storm and maybe a blizzard? No, and we won’t get a white Christmas, assesses the Niels Bohr Institute’s weatherman, meteorologist Aksel Walløe Hansen.

Pressure map over the Atlantic Ocean

On the map you see a widespread low pressure region over the Atlantic Ocean stretching towards Greenland and Canada. There is a high-pressure system of Europe with a centre southeast of Denmark. The weather can only be cold if really cold air builds at the surface in Central Europe and that it is not the case in this particular situation. Consequently, the forecast for Christmas: mild, cloudy/wet and with a bit of wind.

Weather forecasts have gradually reached such a quality that we can make forecasts a week ahead and even longer in certain situations, explains Aksel Walløe Hansen, who would like to make a forecast – here 12 days before Christmas – for the weather on 24 December based on an analysis of weather maps from the American Weather Prediction Center.

“On the maps you can see a widespread low pressure area over the Atlantic Ocean stretching towards Greenland and Canada. There is a high-pressure system of Europe with a centre southeast of Denmark. The weather can only be cold if really cold air has been build up beforehand at the surface in Central Europe and that it is not the case in this particular situation. Consequently, the forecast for Christmas: mild, cloudy/wet and certainly with a bit of wind,” estimates Aksel Walløe Hansen, meteorologist at the Niels Bohr Institute at the University of Copenhagen. 

The storms that struck the country

He has also analysed the two storms we have had in recent months.

On Thursday, 5 December 2013, storm number 2 in the winter season 2013-2014 hit Denmark. Compared with the first storm on 28th of October, the December storm came from a westerly direction. It also had a different course with a more widespread wind system and it lasted longer and caused flooding because og the strong wind over a rather long period and with a wind direction that allowed the water to pile up near the coasts.

“From a meteorologist’s perspective, there are many interesting aspects to such a weather system and the storm on the 5th of December was predicted well ahead of time – eight days,” explains Aksel Walløe Hansen.

Great scientific achievement

“So you could already predict on Thursday the week before that a storm would hit Denmark a week later. Scientifically speaking, this is a great achievement that you would not have been able to do just 10-20 years ago. The efforts of many people lie behind this fine result, both in a huge improvement in the understanding of weather dynamics through many more and better observations of the weather, enormously powerful computers and more sophisticated ways of programming computers. Denmark has contributed to this development,” explains Aksel Walløe Hansen