Tuesday, 14 May 2013

Summer and the role of the jet stream


Batten down the hatches as forecasters warn there are a few wet and windy weeks on the way.

As we nudge into summer, experts have started talking about what we can expect over the next couple of months.

After last year’s washout - the wettest summer for 100 years - many are rightly hoping for a turnaround this year.

The bad news is that early indications suggest we may get a repeat of 2012’s catalogue of misery.

Remember June, July and August? A long, grey dredge of drizzle, rain and chilly winds.

Weather forecasts can only really be close to exact up to 10 days in advance, although long-range forecasters can give a pretty good idea of what is further afield.

They use models based on probability and track the paths of high and low pressure systems to give an indication of what the weather might do in the coming weeks and even months.

The good news is, this can change so although early indications show a miserable summer on the cards, it is not yet a fait accompli.

One of the indicators forecasters use is the jet stream and its position.

The jet stream is a thin ribbon of rapidly-flowing air which circulates around the earth and governs how low-pressure systems, which bring wind and rain, influence our weather.

When it is further north, the jet stream pushes low-pressure away from the UK making it drier and more settled, when the jet stream is further south, its usual winter position, it guides low pressure over the country.

That is a very simplified explanation, and it is a much more complex process, but pretty much sums it up.

Last year the jet stream was wedged much further south than normal for the time of year, hence we saw wetter, cooler conditions throughout the season.

Currently it appears to be doing the same thing, prompting forecasters to place their bets on a repeat of last summer.

However, all is not lost, the jet stream can move, and fingers crossed there may be a glimmer of hope on the horizon - although it is looking  pretty miserable in the near future.

Thanks to the Met Office for this video which explains how the jet stream influences our weather.




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