UK weather: What is a ‘heat dome’ – and how long will Britain’s hot spell last?
The UK is having a late summer burst of hot weather – while parts of the Mediterranean have been experiencing a phenomenon known as a “heat dome”, forecasters say.
Temperatures in Britain could soar as high as 32C (90F) this week, as much as 4C (39F) higher than Ibiza.
Here, Sky News looks at what is causing the unusually warm conditions in the UK and elsewhere in Europe – and whether we are set for an official heatwave.
People enjoy the hot weather in London’s St James’s Park
What is a heat dome?
A heat dome is loosely defined as an area of high pressure that stays over the same area for days, or even weeks.
Hot air is trapped underneath like a lid on a saucepan, pushing temperatures above what’s normal for the time of year.
The heated air expands upwards into the atmosphere, then high pressure from above acts as a lid, meaning it can’t escape and causes the air to subside or sink – creating a dome effect, the Royal Meteorological Society said.
As the warm air sinks, it compresses and heats up, which then traps more heat underneath and clouds are pushed around it, keeping the heat in even more.
Find out the weather forecast for your area
The Met Office says heat domes encourage temperatures “to keep building day on day”.
However, Sky weather meteorologist Dr Chris England said the phenomenon “doesn’t really apply to the current heat of the UK”.
He said that while a heat dome “has been relevant to some of the Mediterranean heat”, the high pressure affecting the UK “is well to the east”.
“Instead, the flow around the high pressure is generally from the south over the UK, bringing heat up from the Mediterranean and north Africa,” Dr England added.
The Met Office says tropical storms in the far western Atlantic, and deep areas of low pressure, have helped to amplify the jet stream over the Atlantic Ocean and has led to high pressure “dominating over the UK”.
Is the UK set for an official heatwave?
The word “heatwave“ is often used to describe any period of sunny weather, but the Met Office defines it as “an extended period of hot weather relative to the expected conditions of the area at that time of year”.
It says the UK experiences a heatwave when it has at least three consecutive days with daily maximum temperatures meeting or exceeding the heatwave temperature threshold – and this threshold varies by UK county.
Sky weather forecaster Kirsty McCabe said official heatwave conditions “will be met this week as temperatures soar over the next few days with a late blast of summer heat, especially for southern parts of the UK.”
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The peak is likely to occur on Wednesday and Thursday with 31C (88F) or even 32C (90F) possible.
The threshold temperature ranges from 25C (77F) in Scotland and Northern Ireland, to 28C (82F) in London and the Home Counties.
But Ms McCabe said “it’s not just hot weather heading our way, a Saharan dust plume will cross the UK, bringing some spectacular sunrises and sunsets”.
Hitting 30C in September “used to happen around once every seven years or less, but has occurred more frequently in the last decade,” she said.
Could we have the hottest day of the year this week?
This year’s highest temperature is 32.2C (90F) at Chertsey on 10 June and Coningsby on 25 June.
Ms McCabe said: “There is a chance we could exceed that this week [Wednesday or Thursday].”
The highest September temperature ever recorded in the UK was 35.6C (96F) in South Yorkshire in 1906.
Is this an Indian summer?
According to the Met Office Meteorological Glossary, an Indian summer is a warm, calm spell of weather that occurs in autumn, “especially in October and November.”
There is, the Met Office says, no statistical evidence to suggest that such warm spells recur at any particular time each year – warm spells during the autumn months are not uncommon.
How long will the UK’s hot weather last?
An amber alert is in place for the whole of England except the North East, where a yellow alert is in place.
The alert, issued by the UK Health Security Agency and the Met Office, is in place until 9pm on 10 September.
Temperatures reached 30C on Monday in southern England and the southeast of Wales, according to the Met Office – and the hot weather will continue through Tuesday, with highs of 31C (88F) expected.
Met Office spokesperson Oli Claydon said: “We will see good sunny conditions through the week with cloudless skies, and some high temperatures by the time we get to Wednesday and Thursday, where we could see 31 maybe 32 degrees.”
The Met Office said temperatures could also hit 31C (88F) on Friday, although there could be more cloudy weather and chances of rain in the far northwest of Scotland.
But the weather conditions could change over the weekend and Mr Claydon said there is “no indication at the moment of another strong heatwave after this”.
He added: “Through the weekend, we start to see some heavy, potentially thundery, showers developing but (they are) only isolated. There is a little bit of uncertainty as we start to get that far ahead.”
Average temperatures are expected to return by the middle of next week.
UK
MasterChef’s Gregg Wallace steps down as Kirsty Wark among 13 who claim he made inappropriate sexual jokes
MasterChef host Gregg Wallace has stepped down over allegations he made a series of inappropriate sexual comments on a range of programmes over 17 years.
Broadcaster Kirsty Wark is among 13 people who have made claims, with Wallace being investigated by MasterChef’s production company Banijay UK.
In an interview with the BBC, the Newsnight presenter, who was a celebrity contestant on MasterChef in 2011, claimed Wallace used “sexualised language”.
“There were two occasions in particular where he used sexualised language in front of a number of people and it wasn’t as if it was anyone engaged with this,” Wark said.
“It was completely one-way traffic. I think people were uncomfortable and something that I really didn’t expect to happen.”
Sky News has contacted Wallace’s representative for comment.
Kirsty Wark. File pic: PA
‘Fully cooperating’
Banijay UK said the complaints were made to the BBC this week by “individuals in relation to historical allegations of misconduct while working with Gregg Wallace on one of our shows”.
The company said the 60-year-old, who has been a co-presenter and judge of the popular cooking show since 2005, was “committed to fully cooperating throughout the process”.
“Whilst these complainants have not raised the allegations directly with our show producers or parent company Banijay UK, we feel that it is appropriate to conduct an immediate, external review to fully and impartially investigate,” the company said.
“While this review is under way, Gregg Wallace will be stepping away from his role on MasterChef and is committed to fully co-operating throughout the process.
“Banijay UK’s duty of care to staff is always a priority and our expectations regarding behaviour are made clear to both cast and crew on all productions, with multiple ways of raising concerns, including anonymously, clearly promoted on set.
“Whilst these are historical allegations, incidences brought to our attention where these expectations are not met, are thoroughly investigated and addressed appropriately.”
A BBC spokesman said: “We take any issues that are raised with us seriously and we have robust processes in place to deal with them.
“We are always clear that any behaviour which falls below the standards expected by the BBC will not be tolerated.
“Where an individual is contracted directly by an external production company we share any complaints or concerns with that company and we will always support them when addressing them.”
Previous investigation
Last month, Wallace responded to reports that a previous BBC review had found he could continue working at the corporation following reports of an alleged incident in 2018 when he appeared on Impossible Celebrities.
Wallace said those claims had been investigated “promptly” at the time and said he had not said “anything sexual” while appearing on the game show more than half a decade ago.
In an Instagram post following an article in The Sun newspaper, he wrote: “The story that’s hitting the newspapers was investigated promptly when it happened six years ago by the BBC.
“And the outcome of that was that I hadn’t said anything sexual. I’ll need to repeat this again. I didn’t say anything sexual.”
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Alongside MasterChef, Wallace presented Inside The Factory for BBC Two from 2015.
Wallace and Anne-Marie Sterpini in 2014. Pic: PA
Wallace has featured on various BBC shows over the years, including Saturday Kitchen, Eat Well For Less, Supermarket Secrets, Celebrity MasterChef and MasterChef: The Professionals, as well as being a Strictly Come Dancing contestant in 2014.
He was made an MBE for services to food and charity last year.
Recorded episodes of MasterChef: The Professionals featuring Wallace will be transmitted as planned, the PA news agency understands.
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