Why has Britain been battered by a series of storms?

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Waves at Ardrossan in Scotland on January 3. Photo: PA

Since the beginning of December, we've been battered by a seemingly endless series of severe storms. Starting on 5 December, four separate storms have lashed the British Isles.

It's been the stormiest December for almost 50 years – since 1969. And in Scotland, it's been the wettest month for over a century, since 1910.

Waves brake at Ardrossan in Scotland on January 3, 2014. Credit: Danny Lawson/PA Wire

So what's going on? It all starts in the Arctic. In winter, there is a big difference in temperatures between the colder Arctic and the warmer tropics. That drives our old friend the jet stream.

That's a narrow band of fast-moving winds high in the atmosphere. At the moment it's sitting in just the right position to guide storms into Britain.

A windsurfer enjoys the stormy conditions in Dorset at the start of 2014. Credit: Andrew Matthews/PA Wire

But not only that, the jet stream can intensify the storms themselves. And stronger storms strengthen the jet stream. It's a positive feedback that can result in just the cluster of storms we've seen in the last few weeks.

But why is this winter so exceptional? The Met Office speculates that it could be linked to something with the magnificent title the quasi-biennial oscillation.

Waves crash onto the beach in Brighton, East Sussex at the start of the year. Credit: Chris Ison/PA Wire

This is another band of fast moving winds 15 miles up over the Equator. Every 14 months these winds change direction and currently they're blowing from the west.

Met office scientists say that could strengthen the jet stream bringing a bigger risk of stormy weather.

Clouds gather over flooded fields outside Deerhurst, Gloucestershire in December. Credit: Tim Ireland/PA Wire

The good news? That oscillation is expected to decline in the next few months. So the stormy weather won't last forever.