23 Jul 2015

Rain and gales expected. Where has summer gone?

The beginning of July started with record-breaking heat, with Heathrow airport in London soaring to 36.7C, making it the hottest July day on record for the UK.

However, it seems that the end of July will have a very different theme: low pressure, rain and strong winds – not what parents of children who are on their school holidays want to hear.

In fact, Friday into early Saturday looks unseasonably wet and windy across central, southern and eastern parts of England, to the point where the Met Office has issued a yellow “be aware” warning.


Where has summer gone?

While there have been occasional days of warmth and sunshine in July, prolonged spells of settled weather have been absent in comparison to the recent summers.

As is often the case, the reason for the mixed weather this month is the speed and position of the jet stream, 30,000ft up in the jet_stream_WZ_wpatmosphere, which drives the weather that we experience at the surface.

In recent weeks, it has generally been over or to the south of the UK, which not only forms areas of low pressure, but pushes them towards us along an atmospheric superhighway.

For the next week, the jet stream is not only go to stay south of us, but it’s also going to pick up speed, which will send a number of low pressure systems across the country.

Rain and gales possible on Friday

The first notable area of low pressure will arrive in the south west of the UK during Thursday night, before pivoting across England and Wales through Friday and into Saturday morning.

rain_warning_MO_wpWhile there is high confidence that an area of low pressure will form, there is considerable uncertainty about how deep it will be. This will influence how far north the rain moves, how heavy it is and how strong the winds are.

At the moment, the heaviest and most persistent rain over England and Wales looks likely to be south of a line stretching from Aberystwyth to Birmingham to Norwich. Any rain north of this line is likely to be lighter and intermittent.

Around 20-30mm of rain is expected in the wettest areas, with a chance that parts of East Anglia and south east England could locally see as much as 60mm, which could potentially cause some localised flooding.

The other hazard could be strong winds, with gusts of as much as 50mph on the coasts and 30-40mph inland.

This may not sound like a lot, but it’s a time of year when trees are in full leaf and there’s a lot of people doing outdoor activities, so there can be impacts at wind speeds lower than at other times of the year.

More rain and wind to follow

Once the first area of low pressure clears on Saturday morning, there’ll be a bit of a lull, before the next area of low pressure arrives on Sunday, bringing more unsettled weather into the first half of next week.

low_chart_MO_wpHowever, eventually next week, the jet stream will start to weaken and push north of the UK, allowing high pressure to build for a time.

This means that later next week, it should turn drier, brighter and a little warmer with lighter winds, although there are no signs of a heatwave anytime soon.

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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