After months of record–breaking heat, Brits have been told to brace for a cold and stormy winter, thanks to the Super El Niño that’s building in the Pacific Ocean.
With the UK separated from the Pacific Ocean by approximately 5,000 miles of land, not to mention the Atlantic Ocean, you might be wondering how El Niño can impact us on British soil.
Now, scientists have explained how warm ocean temperatures in the Pacific send ‘waves’ rippling through the atmosphere.
These waves push the world’s most powerful weather systems – including the jet stream – off their usual course, wreaking havoc on Britain’s winter weather.
This winter, experts predict the jet stream will send storms towards the UK along powerful currents of fast–moving winds.
While it is still too early to say when these storms will occur, the latest weather predictions agree that bad weather is increasingly likely.
Will Lang, chief meteorologist at the Met Office, told the Daily Mail: ‘El Niño conditions increase the chance of storms in late autumn and early winter.
‘It is too early to comment on flood risk this winter, though again some flooding is to be expected and should be planned for in any UK autumn and winter.’
Experts warn that the ‘unprecedented’ Super El Niño will cause wetter and stormier weather in the UK during autumn and winter
From October to November, the Met Office predicts it could start to get colder in the UK
El Niño was officially declared in June, when sea surface temperatures in the equatorial Pacific Ocean climbed 0.5°C (0.9°F) above the long–term seasonal average.
Now, the Met Office suggests that the natural warming of these critical waters could reach 3°C (5.4°F) in the coming months – with noticeable knock–on effects for Britain.
The El Niño Southern Oscillation is a naturally occurring climate cycle that changes between the hot El Niño and cool La Niña phases every two to seven years.
During an El Niño phase, the trade winds that normally carry warm waters away from South America towards Australia slow or even reverse.
This prevents cold water from welling up and leads to a buildup of hot water near the surface in the equatorial and tropical Pacific Ocean.
The buildup of warm water in the Pacific leads to more evaporation and more movement in the atmosphere driven by convection patterns.
That means there is more thunderstorm activity over the central and eastern Pacific, but there are also wider effects that can extend as far as Europe and the UK.
One of the most obvious consequences for the UK is that there is a greater likelihood of storms in the autumn and early winter.
Dr Chloe Brimicombe, a climate scientist from the University of Oxford, told the Daily Mail: ‘El Niño affects the UK weather through long links in the Earth’s weather system, which we call teleconnections.
‘If processes line up, it can make the winter wetter and stormier in Northwest Europe.’
In particular, El Niño interacts with the large–scale circulation patterns of the North Atlantic Oscillation and the fast–moving body of air known as the jet stream.
As hot air rises over the equator, it spreads towards the poles in a complex pattern known as Hadley circulation, leading to modifications in the circulation patterns worldwide.
Professor Emily Black, a meteorologist from the University of Reading, told the Daily Mail: ‘The unusually warm tropical Pacific shifts the regions where intense tropical rainfall occurs, with subsequent effects on global circulation including over the UK.
‘Specifically, the release of heat into the atmosphere during El Niño generates large–scale atmospheric waves that can alter pressure patterns and the Jet Stream over the North Atlantic.
‘In early winter, these changes can favour lower pressure to the west or northwest of the UK and a stronger flow of air from the Atlantic. That brings more weather fronts and more moisture–laden maritime air across the country, increasing the likelihood of rain.’
These changes are most felt in parts of the UK that are most exposed to Atlantic weather systems, though the actual distribution varies from event to event.
Models reveal a ‘clear and sustained increase’ in El Niño conditions, with the latest data showing the sea surface in the equatorial Pacific is now 2.7°C above average
Warm waters in the Pacific Ocean generate large–scale atmospheric waves that can alter pressure patterns and the Jet Stream, leading to more storms in the UK
Likewise, the effects of El Niño in the UK are likely to be more complex and varied than a simple increase in rainfall.
Professor Black explains El Niño usually creates a stormier start to the winter, rather than a stormier winter throughout.
She adds: ‘Even a very strong El Niño does not determine what the UK winter and autumn will be like. Instead, it changes the probabilities of particular weather patterns.
‘For the UK, El Niño tends to increase the likelihood of mild, wet and windy conditions during autumn and the first part of winter, and colder conditions later on in the season.’
Professor Bill McGuire, of University College London, adds: ‘Powerful El Niños typically bring mild, stormy autumns and early winters to the UK, followed by bitter cold, although this isn’t set in stone.’
Experts also point out that it might be too early to know exactly what the impacts of the growing El Niño will be.
Dr Zachary Labe, a climate scientist at Climate Central, told the Daily Mail: ‘Unlike other parts of the world, such as Southeast Asia and North America, the effects of El Niño on Europe, and specifically the UK, are a bit less predictable and more uncertain.
‘A bigger El Niño does not necessarily mean bigger impacts everywhere. The relationship is much more complicated, particularly over the UK, where several other factors influence the jet stream at the same time.’
Experts caution that even an exceptionally strong El Niño, such as we are now seeing, will not produce easily predictable results and the impact on the UK is hard to determine
While storms and wet weather might be concerning, the more pressing worry is actually that El Niño won’t bring enough rain to make up for the summer drought.
With rainfall totals for July at just 26 per cent of the typical average in northwest England and as little as one per cent in the south–east, water companies will be hoping to replenish diminished reservoirs.
Professor Timothy Palmer, a climate physicist from the University of Oxford, adds: ‘Europe is a long way from the tropical Pacific and the impact of El Niño on UK weather is not consistent from one El Niño to another.
‘So we don’t know what to expect this winter, not least because the El Niño event developing is likely to be unprecedented in magnitude.’
Professor Palmer adds that the first ‘credible’ seasonal forecasts for the winter will come in September, but even then, things may remain uncertain.
‘If there is no consistent signal from the various models, then we will have to conclude that we won’t know in September how El Niño will impact winter UK rain, and will have to wait another month,’ he said.
‘But if there is a consistent signal, the water authorities and the government need to act on it with urgency, particularly if the prediction is for below average rain.’
