21 Aug 2013

My bank holiday weather headache

Being a weatherman, there are certain days of the year that are always circled in red marker pen on the calendar. Yes, you guessed it – bank holiday weekends – a time when everyone is hoping for sunshine and warmth to enjoy their extra day off work.

Thankfully, each of the bank holiday weekends so far this year have come up trumps for most of us, but the final one of the year is going to be tricky to get right. There’ll be winners and losers – just to get the bad news out of the way early on.

The fly in the ointment in the coming days will be something called an upper trough. In simple terms, it’s a pattern in the atmosphere around 5 miles up which determines how the weather behaves for us at the surface.

The Coldest Summer In Parts Of The UK For Nearly 20 Years

An upper trough makes the air below it unstable and want to rise. When air rises, the moisture in it condenses and cools, giving cloud and rain.

The added complication this weekend is that the air at the surface over the UK is going to be very warm and humid – meaning that there’s a decent reservoir of potential energy and moisture for some heavy downpours.

However, for this potential energy to be released, the upper trough needs to be in the right place at the right time. It’s the exact position of this upper trough that is in question – hence the uncertainty about the detail this weekend.

What’s the latest forecast?

At the moment, I think that Saturday looks to be the most unsettled day for the greatest number of people. It looks like there’ll be showers or longer spells of rain, with thunder possible.

Whilst Sunday will still see some showers, I think there’ll be fewer of them, with longer spells of sunshine in between.

coastal_sun_g_wpMonday could well be the best day of the bank holiday, with an area of high pressure nudging over the UK, bringing many places a dry day with some sunny spells.

Despite any rain or showers, temperatures won’t do badly at all. Scotland and Northern Ireland will reach 17-22C, with England and Wales around 20-25C.

All of this of course comes with the caveat that it is subject to change, but I’ll of course keep you informed as the weekend draws closer.

In the meantime, there’s more on the Channel 4 Weather website and I’ll be tweeting updates on Twitter – @liamdutton

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