13/09/2016 Weather for the Week Ahead

Let's talk about heat, specifically the remarkable September

heat that some parts of the UK are about to experience.

31 Celsius somewhere in south-east England on Tuesday but above

normal temperatures across much of England, east Wales,

southern and eastern Scotland.

But if we get to 31, that will be the first time that

has happened in September in the UK since 1973,

when Donny Osmond was at number one with the song Young Love.

So how do we get heat like that?

We don't normally generate it in place across the UK,

we bring it in from somewhere hotter through the process of advection.

Once it's in, we reinforce that heat through the power of the sun,

insolation, heating the ground,

the heat radiating back from the ground into the air.

You can have advection but if you don't have the insolation,

you're not going to see that really high bump in temperatures.

For Tuesday, we have the advection, 33 in mainland France.

Follow the arrows, coming from there across many parts of the UK.

Look to Northern Ireland, though.

You don't have the advection of warm humid air from the

continent, it's coming down from the north

so temperatures here just around 15, 16 degrees.

You don't even have the insolation because here and across

western parts of Scotland, you've got a weather front.

That means cloud and outbreaks of rain.

You're not going to get the bump in temperatures being experienced

across much of the rest of the UK with that weather front close by.

Pulses of energy along that weather front will produce outbreaks

of heavy rain at times for west and north-west Scotland,

for Northern Ireland.

A few thundery downpours possible in the west of Wales, south-west

of England, maybe north-east Wales and the West Midlands.

Again, temperatures held down Northern Ireland into the

Western Isles, but for many areas above normal.

Again, that chance of 31, maybe a tad higher in south-east England.

Where you see the day's highest temperatures,

it's where you get the highest overnight temperatures going,

Tuesday night and into Wednesday.

Really unusual for the time of year.

By Wednesday, that weather front has nudged

a little bit further west, it is less active

so we may just see a spike in temperatures in Northern Ireland.

19 in Belfast and the warmth perhaps a bit more widespread.

Coming down a little in south-east England but still very warm

to hot sunshine.

Cloudy, misty possible north and east Scotland, north-east England.

Thursday, the weather front looks like it's going to begin to

reinvigorate so the chance of getting outbreaks of rain

coming back to Northern Ireland, western Scotland.

The chance of a thunderstorm across southern parts of England and

even in the sunshine, the temperature

coming down a few degrees.

But still very warm.

At the end of the week, that weather front gets the message and

finally begins to push eastwards back across the UK,

taking outbreaks of rain, and then a change. Look at the arrows coming

in from the Atlantic, bringing in cooler, fresher Atlantic air.

We are advecting it and see the impact on the temperatures.

They're sinking closer to normal for the time of year.

That sets us up for next weekend. Atlantic flow.

A little bump in the isobars could start to settle things down

on Saturday, meaning fewer showers later in the day.

Those temperatures much closer to normal for the time of year.

Looking further ahead, question marks for Sunday and Monday.

What's left of Tropical Storm Ian out in the Atlantic is going

to do, an area of low pressure coming across the Atlantic on

the jet stream. Many computer models take it well away from us,

we don't need to worry. Some bring it close to the UK,

bringing some of us some wind and rain so we have to watch that.

We will, we will keep you updated.

Once that's out of the way, next week it's an Atlantic influence.

Wet, dry, wet, dry.

Temperatures close to normal for the time of year.

Next week looks typical autumn.

This week, though, looks far from it across many parts of the UK.