Hot next week but not necessarily sunny 21/06/19
The heat will rise next week, as will the humidity and the threat of thunderstorms. A subtle shift in the jet stream will bring a big shift in the feel of our weather. Alex Deakin explains.
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00:00It's been a cool and wet June so far,
00:03but that is about to change.
00:05Temperatures are about to jump up.
00:08Now, I know many of us have been looking forward
00:09to some warmer weather,
00:10but this isn't a spell of pleasant, warm sunshine.
00:14Far from it.
00:15This is a big jump in temperatures.
00:17We really are gonna see the mercury rising
00:19as we go into next week.
00:21For some, it's gonna turn hot, uncomfortably hot,
00:25because the humidity will be building as well.
00:28Difficult conditions for sleeping at night,
00:30and that combination of heat, energy, and humidity
00:33brings the real threat of some violent thunderstorms,
00:37significant downpours, large hail, and gusty winds as well.
00:42What's going on?
00:42Well, let's take a look at the bigger picture
00:44and take a look at what's happened in summer so far,
00:47because if we take a look at the jet stream,
00:50that fast-moving ribbon of air high up in the atmosphere
00:52that tends to dictate our weather patterns,
00:55it's been blocked over much of June so far.
00:58It's been in this kind of shape,
00:59and we call this an omega block
01:02because it's shaped like the Greek letter omega.
01:05Now, this means the weather doesn't shift very far,
01:07and it's in this little dip, if you like,
01:09that low-pressure systems develop,
01:11and we've had a low-pressure system
01:13sitting across the UK for much of the month.
01:15That's why it's been wet, and that's why it's been cool.
01:19As we go into next week,
01:20things aren't changing dramatically,
01:22but we are seeing a shift,
01:23a subtle shift in the jet stream.
01:25It's gonna be moving itself a little bit further west,
01:28keeping that same blocked pattern,
01:31but just that subtle shift could have big, big impact
01:34because it's in here where the low-pressure systems
01:37are likely to sit.
01:39So with a low down further to the southwest of the UK,
01:42that is allowing hot air to be drawn up,
01:45not just from France, not just from Spain,
01:46but actually from North Africa.
01:48This is hot air heading our way.
01:52Let's take a closer look at that heat
01:53as it builds over the next few days.
01:56Temperatures will be rising through the weekend,
01:57so it will be quite pleasant on Saturday.
01:59By Sunday, here's the UK.
02:01You can see that hot red air across France and across Spain.
02:05Let's zoom in a little bit because, as I said,
02:07on Sunday, temperatures starting to rise,
02:09but let's run through the sequence over the next few days,
02:12and you can see pulses of hot air,
02:15the darker orange colors moving across the UK.
02:17We'll see that first pulse really on Sunday night
02:20that will spark some thunderstorms,
02:21and then further pulses of hot air
02:24during Tuesday and Wednesday.
02:27The heat, the humidity likely to cause some problems.
02:30As I said at the start,
02:31likely to cause some big thunderstorms.
02:34These thunderstorms will be slightly different,
02:37more intense beasts to the ones
02:39that we've seen over recent weeks.
02:41With more energy comes the potential for more heavy rainfall.
02:45So we are talking about violent storms,
02:48possibly dropping a month's worth of rain
02:51in an hour or so,
02:51torrential rain falling onto saturated ground.
02:55So that could cause some flooding,
02:56large hailstones, potentially damaging hailstones,
02:59and also the potential for some violent gusts
03:01of winds as well.
03:03So yes, temperatures are rising.
03:04It is gonna be warmer.
03:06There will still be some sunshine,
03:08but there is the potential also
03:10for some pretty nasty weather out and about.
03:12Now, there are already warnings in force,
03:14but if you're in a warning area,
03:16it doesn't necessarily mean you're gonna catch
03:18one of those thundery downpours.
03:19They will be hit and miss.
03:21So forecasting for individual events or locations
03:25is quite tricky at this lead time.
03:26Of course, it's Glastonbury next week.
03:28We know about Glastonbury is that it's likely
03:30to be a lot warmer, a lot more humid than it has been.
03:33Take your sunscreen if you're going
03:35because the sun will be strong when it comes out,
03:37but there is the potential for those big storms
03:40in the area as well.
03:42As I said, there's still some uncertainty,
03:44and there's always gonna be difficulty
03:46pinning down the details as we go
03:48and look at these thundery downpours.
03:50So the main message at the moment
03:52is stay tuned to the very latest.
03:54We'll be giving you details of exactly how hot
03:57and exactly where that heat is likely to be next week
03:59over the coming days.
04:01One of the best ways to stay up to date
04:02is to follow us on social media.