Why’s it been so cold?

If you didn’t know, Britain’s been a tad on the chilly side recently. Even all the way down here in Exeter it’s almost reached -17°C.

So why has it been so teeth chatteringly cold? Well, I’m going to answer this with the basic and limited knowledge I already have. It depends on a number of factors. The big factor is the jet stream. A fast moving belt of wind high up in the atmosphere. I won’t go into the physics of how, why and what’s going on but the stream sometimes moves and meanders here and there, much like a river.

This moves for several different reasons. The Sun also has an effect of the jet stream, and this is what a lot of people think may have happened recently – the flood in Pakistan and so on. 

Usually the jet stream is as in (a) bringing warm air and all our standard autumn/winter depressions. The jet stream moved over to what’s shown in (c) though. Dragging freezing cold air down from the north. Give a couple of clear nights and the country starts feeling like Russia. A front that comes through will turn into snowy precipitation and huzzah – here we are now.

This lovely CuNim popped across the airport the other day and dumped a nice load of snow. Conveniently just after the runway had been cleared!

Yesterday morning, 26/12/2010, at 9am Exeter was the 5th coldest spot, according to the Met Office, in the country. Temperatures down to -13.4°C. Nice!

It seems as if the jet stream has come to its senses today. Winds coming up from the south, bringing warmer air and so rain to wash away the snow and ice.

It doesn’t look like it’s going to stay like that for long though. I’d recommend keeping the hat, gloves and maybe even the thermals within arms reach for a while yet.

Hope you all had a good Christmas and enjoy your New Years parties!

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