12 Sep 2013

Warnings issued for first autumn storm expected this weekend

The first autumn storm of the season is expected later this weekend, with a deep area of low pressure sweeping just to the north of the UK on Sunday.

Heavy rain and gales are expected in many areas – especially in the north, where Scotland and Northern Ireland are at risk from gusts of wind as strong as 70mph.

The expected stormy weather follows a brief burst of warmth at the beginning of September, after which the weather has been gradually sliding into autumnal mode.

Temperatures have struggled to reach 20C over the past week, with most of us seeing cloud, wind and rain at some point.


A speedy jet stream

The cause of this change to stormy weather is the position and speed of the jet stream – the fast-moving ribbon of air five miles above our heads that determines the weather that we experience at the surface.

Not only is the jet stream going to dip south of the UK in the coming days, it’s also going to speed up and reach speeds of around 180mph 30,000 feet up in the sky.

z_autumn_storm1_wpThe consequence of such a fast-moving jet stream racing towards us is that it sucks air up from the surface. With air rising so quickly, it causes pressure to fall rapidly, aiding the formation of a deep area of low pressure.

It’s the southerly position of the jet stream that then steers this stormy weather towards us, bringing with it heavy rain, gales and colder air.

How windy will it be?

The winds across the UK will pick up during Sunday daytime and are likely to peak overnight into the first part of Monday, with Met Office warnings issued.

Scotland, Northern Ireland and the far north of England will see winds gusting 45-60mph, with gusts as strong as 70mph around coasts and over the hills.

For the rest of England, along with Wales, winds are likely to gust 35-50mph, with hills and mountains touching 60mph.

Potential hazards

The difficulty at this time of year is that there are still lots of leaves on the trees. Leaves act as sails with their large surface area, catching the wind and resulting in branches being broken off and, in the worst case scenario, trees being blown down.

forth_bridge_g_wpAlso, having only had some pleasant summer weather a few weeks ago, lots of garden furniture will still be outdoors. It is worth putting down parasols and stowing things away to avoid them being blown around.

The combination of heavy rain and strong winds may also cause some problems to transport – especially exposed road bridges and high-sided vehicles.

Don’t forget, you can get the latest forecast on the Channel 4 Weather website. I’ll also be posting updates on Twitter – @liamdutton

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