Week Ahead 19/08/2024 – Jet stream powers up
This is the Met Office UK Weather forecast for the week ahead 19/08/2024. As the jet stream increases in strength and Atlantic ex-hurricanes come into play, the UK's weather takes an unsettled turn this week. Bringing you this weekend’s weather forecast is Aidan McGivern
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00:00Hi there and welcome to the Met Office forecast for the week ahead. It might be August, still
00:05technically summer, but depending where you are in the UK it may feel at times this week
00:10like autumn has arrived early. The reason behind the more unsettled weather we are expecting
00:15this week is an increasingly powerful jet stream and the reason for an increasingly
00:21powerful jet stream is something we often see at this time of year actually is an enhanced
00:27temperature contrast across the North Atlantic. That's what helps to fuel the jet stream and
00:31we've got this tremendous mass of very warm waters across the tropics and the subtropics
00:39and then we've got this increasingly cold air sinking south across the Davis Strait
00:44and Greenland and where these two air masses collide of course you get increased power
00:49to the jet stream and that's especially going to be the case by the end of the week as that
00:54jet stream picks up and develops as well as sends areas of low pressure towards the
01:00UK. It's north-western parts that will bear the brunt of the wind and rain this week,
01:05drier and less windy towards the south-east but all areas expecting very changeable weather
01:11from day to day and from place to place. Now we start off Tuesday with some sunshine first
01:18thing through the Midlands and to parts of central and southern England. Elsewhere a
01:21number of showers from the word go and those showers will rapidly push into northern and
01:26western parts of the UK through the day. The most frequent and most prolonged downpours
01:30will be across western Scotland, north-west England, northern Ireland along with some
01:34very gusty winds and it's going to feel cool where that happens, there'll be a rumble of
01:38thunder as well, these showers are going to be lively. Further south-east, drier and some
01:43parts of say the east Midlands, eastern and southern England will largely avoid the showers
01:48with some sunny spells in between and where we get that sunshine feeling pleasant enough
01:53but obviously where we've got the wind and the showery rain feeling much less pleasant
01:58for the time of year. It's not unusual at this time of year for hurricanes in the Atlantic
02:03to influence the UK's weather in some shape or form. Hurricane Ernesto brought some damaging
02:09impacts to parts of the Caribbean last week, now it's moving north and as it pushes into
02:15cooler north Atlantic waters of course it will no longer be a hurricane, it will diminish
02:21in nature, it will become a more typical Atlantic low and even just merge into a cold front
02:27rather than becoming a defined feature in itself. So in that way this ex-hurricane or
02:34at least the remnants from this ex-hurricane will be no different from other areas of low
02:39pressure or weather fronts that we often see coming in from the west. But there's one important
02:44difference and that is its origins, the tropical origins of this means that we're going to
02:49see a lot of tropical humid air move into the UK and dump a lot of moisture and that
02:56means that north-western parts during Wednesday and Thursday will be very sodden and west-facing
03:01hills of western Scotland in particular will see an awful lot of rainfall, parts of Argyll
03:06and West Highland more than 100mm of west-facing hills yellow rain warning in force. So we
03:13start off Wednesday dry before that rain arrives but already from the word go cloud thickening
03:19across western parts, some light showery rain pushing in but then really it's from lunchtime
03:25that we'll see the more persistent stuff arrive into western Scotland, Northern Ireland, north-west
03:29England and North Wales seeing that rainfall by the end of the afternoon. Clouding skies
03:35elsewhere but staying mostly dry towards the south and south-east, lighter winds here whilst
03:39the winds really pick up strength across the north-west of the UK, 50 perhaps 60mph
03:45or more as far as the wind gusts are concerned across the north and west of Scotland and
03:49that's the way the very strong winds pushes through the Irish Sea. Later Wednesday into
03:53the start of Thursday. The rain threw out much of daylight on Wednesday, mostly persistent
03:59but light to moderate. It's really into Thursday that the rain turns especially heavy and those
04:06rainfall totals are going to mount up through Wednesday and into Thursday across western
04:12Scotland in particular. I think south-west Scotland 50mm of rainfall in places but Argyll
04:17and West Highland of west-facing hills the risk of more than 100mm of rain through this
04:22period that could cause some localised flooding, yellow rainfall warning in force. The band
04:28of rain moves south-east and really diminishes in nature. It becomes light and patchy by
04:33the end of Thursday with showers and brighter interludes following in the north-west and
04:38staying blustery although the strongest of the winds by this stage will have moved through.
04:41So breezy, cloudy, some light outbreaks of rain into parts of England and Wales by the
04:47end of Thursday but nowhere near as heavy or as persistent as compared with Scotland.
04:53And that shows up on this rolling rainfall totals graphics. So we're starting Monday
04:57and we're moving through to Friday and seeing those rainfall totals mount up with the key
05:02there on the right of the screen and you can see how the rain really adds up across parts
05:09of Scotland, Northern Ireland, north-west England, parts of Wales as well but really
05:12the hills are showing up very nicely on this graphic indicating that a lot of the rainfall
05:19will be most enhanced over higher parts of western UK with a marked rain shadow across
05:24eastern Scotland and more especially eastern England. Very little rainfall in places towards
05:30the east and south-east with more than 100mm through the week over some of those west-facing
05:35hills of western Scotland. So marked contrasts north-west to south-east in the rainfall distribution
05:41and that continues as we end the week with the front associated with ex-hurricane Ernesto
05:47moving through and then the next low coming along picked up by the jet stream deepening
05:53during Thursday and into Friday and bringing another swathe of strong winds and heavy rain.
05:59Now there are some uncertainties because we're still four or five days out with the
06:04track and depth of this low but suffice to say it's going to bring another day of unsettled
06:08weather across the UK. For the word go we've got cloud thickening and outbreaks of heavy
06:13and persistent rain moving into much of the country. Perhaps the rainfall bit focused
06:18more to the south compared with Wednesday and Thursday's wet weather so Wales, western
06:24England seeing some particularly wet weather. That moves through followed by showers and
06:29some brighter interludes. The winds strong through Friday as well making it feel unseasonably
06:34cool and once that low's out of the way we've still got this changeable westerly air flow.
06:40We've still got a powerful jet stream in charge through the weekend so the weather's going
06:44to stay changeable or unsettled on Saturday and Sunday with further showers, longer spells
06:49of rain and blustery winds. Autumn may have started early but of course summer has still
06:57got some legs to it and next week, the last week of August we may see a slight change
07:04to warmer weather. So there's always some hope I suppose if you don't like this kind
07:09of weather. More on our YouTube channel, make sure you subscribe so you never miss an update.
07:13Bye bye.