0:00:03 > 0:00:06Let's talk about heat, specifically the remarkable September
0:00:06 > 0:00:08heat that some parts of the UK are about to experience.
0:00:08 > 0:00:1231 Celsius somewhere in south-east England on Tuesday but above
0:00:12 > 0:00:15normal temperatures across much of England, east Wales,
0:00:15 > 0:00:17southern and eastern Scotland.
0:00:17 > 0:00:19But if we get to 31, that will be the first time that
0:00:19 > 0:00:23has happened in September in the UK since 1973,
0:00:23 > 0:00:26when Donny Osmond was at number one with the song Young Love.
0:00:26 > 0:00:28So how do we get heat like that?
0:00:28 > 0:00:30We don't normally generate it in place across the UK,
0:00:30 > 0:00:34we bring it in from somewhere hotter through the process of advection.
0:00:34 > 0:00:37Once it's in, we reinforce that heat through the power of the sun,
0:00:37 > 0:00:39insolation, heating the ground,
0:00:39 > 0:00:41the heat radiating back from the ground into the air.
0:00:41 > 0:00:44You can have advection but if you don't have the insolation,
0:00:44 > 0:00:47you're not going to see that really high bump in temperatures.
0:00:47 > 0:00:51For Tuesday, we have the advection, 33 in mainland France.
0:00:51 > 0:00:55Follow the arrows, coming from there across many parts of the UK.
0:00:55 > 0:00:56Look to Northern Ireland, though.
0:00:56 > 0:00:59You don't have the advection of warm humid air from the
0:00:59 > 0:01:01continent, it's coming down from the north
0:01:01 > 0:01:04so temperatures here just around 15, 16 degrees.
0:01:04 > 0:01:07You don't even have the insolation because here and across
0:01:07 > 0:01:10western parts of Scotland, you've got a weather front.
0:01:10 > 0:01:12That means cloud and outbreaks of rain.
0:01:12 > 0:01:15You're not going to get the bump in temperatures being experienced
0:01:15 > 0:01:18across much of the rest of the UK with that weather front close by.
0:01:18 > 0:01:22Pulses of energy along that weather front will produce outbreaks
0:01:22 > 0:01:25of heavy rain at times for west and north-west Scotland,
0:01:25 > 0:01:26for Northern Ireland.
0:01:26 > 0:01:29A few thundery downpours possible in the west of Wales, south-west
0:01:29 > 0:01:33of England, maybe north-east Wales and the West Midlands.
0:01:33 > 0:01:35Again, temperatures held down Northern Ireland into the
0:01:35 > 0:01:37Western Isles, but for many areas above normal.
0:01:37 > 0:01:41Again, that chance of 31, maybe a tad higher in south-east England.
0:01:41 > 0:01:43Where you see the day's highest temperatures,
0:01:43 > 0:01:46it's where you get the highest overnight temperatures going,
0:01:46 > 0:01:47Tuesday night and into Wednesday.
0:01:47 > 0:01:49Really unusual for the time of year.
0:01:49 > 0:01:51By Wednesday, that weather front has nudged
0:01:51 > 0:01:54a little bit further west, it is less active
0:01:54 > 0:01:57so we may just see a spike in temperatures in Northern Ireland.
0:01:57 > 0:02:0119 in Belfast and the warmth perhaps a bit more widespread.
0:02:01 > 0:02:04Coming down a little in south-east England but still very warm
0:02:04 > 0:02:06to hot sunshine.
0:02:06 > 0:02:09Cloudy, misty possible north and east Scotland, north-east England.
0:02:09 > 0:02:12Thursday, the weather front looks like it's going to begin to
0:02:12 > 0:02:15reinvigorate so the chance of getting outbreaks of rain
0:02:15 > 0:02:17coming back to Northern Ireland, western Scotland.
0:02:17 > 0:02:20The chance of a thunderstorm across southern parts of England and
0:02:20 > 0:02:22even in the sunshine, the temperature
0:02:22 > 0:02:23coming down a few degrees.
0:02:23 > 0:02:25But still very warm.
0:02:25 > 0:02:28At the end of the week, that weather front gets the message and
0:02:28 > 0:02:30finally begins to push eastwards back across the UK,
0:02:30 > 0:02:34taking outbreaks of rain, and then a change. Look at the arrows coming
0:02:34 > 0:02:38in from the Atlantic, bringing in cooler, fresher Atlantic air.
0:02:38 > 0:02:41We are advecting it and see the impact on the temperatures.
0:02:41 > 0:02:43They're sinking closer to normal for the time of year.
0:02:43 > 0:02:46That sets us up for next weekend. Atlantic flow.
0:02:46 > 0:02:50A little bump in the isobars could start to settle things down
0:02:50 > 0:02:52on Saturday, meaning fewer showers later in the day.
0:02:52 > 0:02:56Those temperatures much closer to normal for the time of year.
0:02:56 > 0:02:59Looking further ahead, question marks for Sunday and Monday.
0:02:59 > 0:03:03What's left of Tropical Storm Ian out in the Atlantic is going
0:03:03 > 0:03:05to do, an area of low pressure coming across the Atlantic on
0:03:05 > 0:03:08the jet stream. Many computer models take it well away from us,
0:03:08 > 0:03:10we don't need to worry. Some bring it close to the UK,
0:03:10 > 0:03:14bringing some of us some wind and rain so we have to watch that.
0:03:14 > 0:03:15We will, we will keep you updated.
0:03:15 > 0:03:18Once that's out of the way, next week it's an Atlantic influence.
0:03:18 > 0:03:21Wet, dry, wet, dry.
0:03:21 > 0:03:24Temperatures close to normal for the time of year.
0:03:24 > 0:03:26Next week looks typical autumn.
0:03:26 > 0:03:29This week, though, looks far from it across many parts of the UK.