14/09/2016 Weather for the Week Ahead

What a day Tuesday was, remarkable weather for different reasons,

depending on where you are, but under the heading of "extreme".

First of all, extreme heat, 34 Celsius in Kent,

the highest temperature of the year, the highest in September since...

Well, yesterday I said if we got to 31, it would be the hottest

in September since Donny Osmond was at number one in 1973,

but you have to go back to 1911 to get a temperature higher than

this in the UK in September.

We were going to the music hall then to get the latest hits.

So there's your headline figure of 34 in Gravesend,

but that's exceptional in mid-September.

In Hull, 30. But there are the contrasts, Belfast 18, Glasgow 17

and, for some, torrential thunderstorms.

This is what went through Manchester on Tuesday evening,

causing the postponement of that Champions League game.

The weather contrasts because of a stuck weather pattern with

a weather front close to western Britain with outbreaks of

rain on it, but ahead of it we're still drawing up that very warm,

humid air from the Continent.

And to look at the reasons for a stuck weather pattern,

we look at the jet stream this week,

and it has a big dip in it, then it rides high to the north of the UK.

It is a highly amplified pattern of the jet stream we call "meridional".

And whenever you have a meridional jet stream pattern,

it's prone to atmospheric blocking. Nothing is moving any time soon.

You end up with almost the weather stuck in time.

But the weather pattern is going to change,

finally, going into the weekend, and we'll look at that in a moment.

First of all, to Wednesday, first to that weather front to the west.

Not as active on Wednesday, a little rain to Northern Ireland

and northern Scotland. England and Wales looking mainly dry.

A warmer day in Wales and western England,

a cooler day in south-east Scotland, north-east England.

Still near 30 in the hottest parts of south-east England,

East Anglia and into the East Midlands.

On Thursday, the weather pattern's still the same.

We still have that weather front, we're still drawing in some warmth

ahead of that from the weather front, parts of Northern Ireland

and Western Scotland at risk of seeing some rain moving in.

Still some warm, sunny spells elsewhere,

and still the highest temperatures near 30.

But Thursday night into Friday, very wet weather potentially for

Scotland, northern England as the front moves eastwards across

the UK, clearing Friday to allow Atlantic air to move back in.

That's a big change in how the weather feels, so temperatures

are coming down, it will feel much fresher as the humidity disappears.

The start of the weekend,

a brief ridge of high pressure for England and Wales, but

a weather front to the north of the UK looks like it will bring

some outbreaks of rain and brisk winds into parts of Scotland

and Northern Ireland.

England and Wales, at this stage, for Saturday looking mainly dry.

Look at those temperatures, close to normal for the time of year.

Sunday, I mentioned it yesterday, former Tropical Storm Ian

looks like it's converging in its movement

between Iceland and Scotland,

picking up the winds north-west of Britain on Sunday and bringing

a band of wet weather in from the west, but it looks as if this former

tropical weather system will not

produce anything exceptional for the UK.

So, you get the idea. Things are starting to become more mobile, and

that's the change in the jet stream pattern lasting into next week.

We've lost the big dips, and the ridges are just moving across the

Atlantic towards us, a more zonal pattern,

and that means a more changeable pattern in our weather.

As weather systems can come on through, nothing is being blocked.

So, what we can expect next week is, well,

a bit of autumn in our weather. Nothing too extreme.

It looks like it'll be changeable, occasionally wet,

occasionally dry, the humidity gone

and temperatures closer to normal for the time of year,

a weather pattern which is finally

suited to the time of year. And that's it for now.