13 Dec 2012

Wet and windy weather to make a return

At the end of last week, I wrote a blog about how the first notable cold snap of the winter would arrive this week. Whilst it has arrived, on this occasion, it’s going to be short-lived, with wet and windy weather set to make a return in the next 24 hours.

Even though the past few days have been cold, there has been no significant snow, with just a few light flurries here and there. This shouldn’t come as a surprise, as in my blog last week I highlighted that the detail with regard to snow was very uncertain.

So, why hasn’t this cold snap lasted for very long? Well, once again, it is down to the position and speed of the jet stream.

Last week, I explained that the jet stream was expected to split into two, with one branch heading north towards Greenland, and the other heading south towards Iberia and northern Africa.

This jet stream allowed a blocking high to form, but this time the block was weak and didn’t build as strongly as some weather computer models were hinting at last week. This has been due the lack of power in the northern branch of the split jet stream.

If it had been more powerful, there would have been a stronger surge of warm air northwards towards Greenland, which would have built a stronger blocking high – something in meteorology know as ridge amplification.

Subsequently, with a stronger blocking high, colder air would have been pushed across the UK from mainland Europe for longer, bringing a more prolonged cold snap.

Instead, the jet stream has roared back to life across the Atlantic ocean, which will bring a number of low pressure systems to our shore, along with heavy rain and gales.

Thankfully, with the winds being strong, it means that the heavy rain should generally move through relatively quickly, reducing the risk of flooding.

However, we are approaching high tides, so with strong onshore winds for southern coasts of England and Wales in the coming days, there could be coastal flooding – something highlighted in the Environment Agency’s three-day flood risk forecast.

Whilst this weekend will be mild, with temperatures reaching into double figures, it will turn cooler again next week. But, with daytime temperatures in the range of 4-8C, any wintry weather will probably be confined to the hills and mountains.

Don’t forget, you can get the latest five day forecast on the Channel 4 Weather website and you can follow my regular updates on Twitter – @liamdutton

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