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Scientists comment on Storm Eowyn, after weather warnings have been issued across the UK and Northern Ireland.
Prof Suzanne Gray, Professor of Meteorology, University of Reading, said:
“Storm Éowyn is currently forecast to become one of the deepest storms on record in the UK, with the central pressure dropping to below 940 millibars as the storm approaches the west coast of Scotland. Pressures below 940 mb are rare for the British Isles, with only five reliably recorded occasions of pressures below 940 mb on the mainland British Isles in 200 years of reliable measurements up to 2007.
“Storm Dirk, which occurred on Christmas Eve 2013, was a recent record breaker for storm pressure. Its central pressure drop to 927 mb as it approached North West Scotland made it the deepest storm in the vicinity of the British Isles since 1886. While Storm Éowyn is not forecast to beat this record, it is certainly a storm to watch.
“Stormy weather is not unusual in the autumn and winter over the UK. It requires detailed research to attribute the strength of the impacts of any specific storm to climate change. To date, the observed trends in UK storminess have not provided a conclusive link with climate change. One reason why is it difficult to make this link is that the position and variability of UK storminess is very dependent on the position of the jet stream, which varies substantially. However, studies have shown that winter storms may become more frequent and clustered in the future, such that several storms occur one after the other. The intensity of rainfall is likely to increase but it is unclear how the overall intensity will change because of competing effects. The small number of studies that have considered the “sting jets” that can produce particularly strong localised surface winds and gusts have found an increasing likelihood that they will occur in storms.”
Dr Carola Koenig, flood and climate change expert, Brunel University of London’s Centre for Flood Risk and Resilience, said:
“With storm Éowyn making landfall, most of the UK will be affected by strong winds and heavy rain, particularly on Friday which has red weather alerts in place, mostly for northern regions.
“Residents are advised to follow MET Office advice and prepare. This includes knowing how to shut off electricity and gas, having emergency numbers to hand and having an emergency bag packed which should include required medicine, warm clothing and blankets. For further helpful advice, see Protecting property from flooding – Met Office1.”
Dr Nicholas Leach, postdoctoral researcher within the Predictability of Weather and Climate research group, University of Oxford, said:
What do we know about this storm and is it expected to be damaging?
“Éowyn is an extratropical cyclone that has formed in the North Atlantic.
“It is forecast to be a “bomb” cyclone that has intensified extremely rapidly.
“Bomb cyclones are typically the most impactful winter storms in Northern Europe. Other recent notable bomb cyclones include Eunice in 2022 and Ciaran in 2023.
“Éowyn is likely to cause potentially severe damage along the West coast of Ireland and across Northern Ireland and Western and Southern Scotland.
What does an amber or a red warning mean?
“An amber warning means that widespread disruption is expected from impacts such as:
– flying debris causing injury and may pose a danger to life;
– power cuts;
– transport infrastructure damage;
– damage to buildings, especially rooves.
“I note that the Met Office has upgraded the amber warning to red for parts of Northern Ireland and West Scotland:
– Fallen trees are very likely to cause extremely dangerous driving conditions;
– Flying debris including roof tiles causing a risk to life;
– Red weather warnings are rarely issued and it is crucial that people check for updates and stay safe – for example by avoiding travelling if at all possible.
What causes storms like these?
“Storms like Éowyn typically form along the boundaries between high and low atmospheric temperatures, in this case along a cold front in the North Atlantic.
“The cold air behind the front sinks, forcing the warm air to rise. The displacement of the warm air creates a low pressure center, drawing more air in.
“Feedbacks from air temperature and humidity gradients further fuel the intensification of the low pressure system and associated high winds and precipitation.
Is there anything unusual about this one or is it a standard winter storm?
“Éowyn looks like an archetypal extratropical winter storm based on how it has formed out of a cold front in the North Atlantic.
“However, its intensity is unusual. Its central pressure, which is often how meteorologists measure storm intensity, is forecast to drop to 940 hPa, which would rank it among the most intense storms on record in the UK. This would be the lowest pressure over the UK since 1982. It’s also worth saying that just because a storm is intense from a meteorological perspective it doesn’t mean it will be severely damaging – which also very strongly depends on where the storm tracks.
“It has undergone exceptionally rapid cyclogenesis, at around double the rate required for explosive cyclogenesis.
“The wind speeds forecast are also very unusual. Wind gusts of over 170 mph have been forecast offshore, with gusts of well over 100 mph forecast onshore along the West Coast of Ireland.
Climate change and extratropical cyclones
“Although the impacts of climate change on extratropical cyclones are still uncertain, there have been a number of recent studies that have suggested the strongest storms (such as Éowyn) may get stronger with climate change.
“In a study1 published last year led by a colleague, Shirin Ermis, we showed, using a state-of-the-art weather forecast model, that in a counterfactual warmer climate, Storm Eunice would have been significantly stronger and wetter.
“This is due to the additional humidity in the atmosphere causing increased latent heating, thus intensifying the storm more than otherwise.”
1 https://iopscience.iop.org/article/10.1088/2752-5295/ad4200
Dr Sarah Kew, Researcher at the Royal Netherlands Meteorological Institute and co-lead of World Weather Attribution, said:
“According to a recent World Weather Attribution study1, Winter and autumn storms are depositing about 20% more rainfall in the UK and Ireland due to climate change.
“The influence of climate change on storm winds is less clear. Studies have identified small increases or decreases in storm winds in the UK and Ireland using different datasets and climate models, but more research is needed.
“A warmer climate is not a good thing for the UK and Ireland. With only 1.3°C of warming, autumn and winters are significantly wetter. As temperatures rise, this effect will worsen – heavier rainfall will impact all aspects of life, from homes and farms to stormwater systems, transport networks, and football pitches.”
Dr Chris White, Reader in Engineering for Extremes; and Head of the Centre for Water, Environment, Sustainability and Public Health, University of Strathclyde, said:
“Red warnings are rare; they only get issued only when there is a high chance of impacts and a risk to life.
“Storm Éowyn is a potentially dangerous ‘multi-hazard’ event – a combination of very strong winds, heavy rain and snow – which can produce a wide range of impacts.
“The exact impacts of these types of storms are challenging to forecast, however, which makes them particularly challenging to prepare for and manage. We are in for a potentially wild day here across Scotland’s central belt.”
Dr Ambrogio Volonté, Senior Research Fellow, Department of Meteorology, University of Reading, said:
“Storm Éowyn is shaping up to be an impressive storm, rapidly intensifying as it races east across the North Atlantic. It is set to make landfall over Ireland in the early hours of Friday, before sweeping across the British Isles throughout the day. Gusts are predicted to exceed 100mph in exposed areas on Ireland’s west coast. Storm Éowyn could rival the ferocity of Storm Eunice and Storm Ciarán, both of which sadly claimed lives and left behind severe damage.
“The storm is “explosively developing,” meaning it’s intensifying at an exceptional rate. Its central air pressure is expected to plummet by over 50hPa in just 24 hours – more than twice what’s needed for meteorologists to classify it as explosive. This rapid strengthening happens when a powerful jet stream high in the atmosphere combines with a sharp contrast in temperatures and moisture at the ocean’s surface, creating the perfect conditions for the system to grow into a particularly intense and dangerous storm.
“In fact, Storm Éowyn’s structure mirrors some of the most formidable storms of recent decades, and its predicted intensity puts it firmly in the ranks of the strongest we’ve experienced. With such extreme winds on the horizon, Met Éireann and the Met Office have issued important warnings so people can appropriately prepare for widespread disruption and damage.”
Prof Liz Bentley, Chief Executive, Royal Meteorological Society, said:
What do we know about this storm and is it expected to be damaging?
“Storm Éowyn is a rapidly deepening low pressure system developing to the west of the UK and will quickly move across the UK during Friday with peak wind gusts of 80-90mph across Northern Ireland, North Wales, Northern England and Southern Scotland and some exposed locations could record 100mph gusts. These are damaging strength winds and there is a danger to life from flying debris, large waves near the coast, fallen trees and damage to building and the Met Office has issued rare red warnings.
What does a red warning mean?
“It is rare for the Met Office to issue red warnings. They are the highest level of weather warning and indicate that dangerous weather is expected and there is a danger to life. People living or travelling in the area under the red warnings are encouraged to take action to keep themselves and others safe from the impact of the severe weather, in the case of Storm Éowyn that impact is from strong winds. In addition to the risk to life there is also the likelihood of substantial disruption to travel, energy supplies and damage to building and infrastructure. People there should avoid travelling if at all possible and follow the advice of the emergency services and local authorities.
What causes storms like these?
“The jetstream, which is a band of strong winds at the top of the atmosphere around 30,000ft above the ground, provides the mechanism for storms, like Storm Éowyn, to develop. The jetstream in winter is often stronger leading to more storms forming, and its position is often closer to the UK so those developing systems are directed towards our shores.
“The current maximum speed in the jetstream is more than 250mph and data from flightradar24 highlighted that a flight BA from Las Vegas to Heathrow hit a speed of 814mph thanks to the strong tailwind in the jetstream. The subsonic speed record currently stands at 835mph, so that record could well be broken in the coming hours.
Is there anything unusual about this one or is it a standard winter storm?
“Storm Éowyn is a particularly potent storm particular because of a very active Jetstream, also the storm will be at its strongest as it crosses the UK and Ireland.”
Dr Jess Neumann, Associate Professor of Hydrology, University of Reading, said:
“Storm Éowyn is not one to underestimate – stay safe, stay prepared, and plan ahead. This storm has the potential to bring serious risks, not just to travel and property, but to your safety and wellbeing.
“Storm Éowyn is set to hit the UK hard on Friday, bringing 90mph winds, torrential rain, and potentially leaving heavy snow in its wake.
“Expect widespread travel disruption, power outages and dangerous conditions along coastlines and high wind areas. Severe flooding is likely, with heavy rain and snowmelt combining to create hazardous surface water and flash floods that could strike with little warning. Check your flood risk online at https://www.gov.uk/check-flooding and take action now if you’re in a vulnerable area.
“If you must travel, be prepared for delays. Carry spare warm clothes, blankets, bottled water, a torch, and ensure your vehicle is fuelled and well-maintained. For those at risk of flooding, act quickly. If time permits and it’s safe, turn off your gas and electricity, move valuables to higher ground, and relocate to safety.”
Prof Daniela Schmidt, Professor of Earth Sciences, University of Bristol, said:
“Climate changes is too often reduced to warming, and numbers which are small compared to the seasonal changes in temperature, giving a false sense of security.
“Climate change also changes how much vapour is in the atmosphere, how strong our storms become, how frequent they are, and how much flooding this has the potential to cause.
“We need to learn from disaster risk reduction to be better prepared for these events, and early warning is a very important part of this preparedness. We need to look out for those most vulnerable, who might not hear these warnings, do not understand them, or cannot act. And ultimately, we need to adapt and reduce our emissions as these storms, fires, droughts are just the beginning of we do not prioritise action.”
Prof Tim Palmer, Royal Society Research Professor Emeritus, University of Oxford, said:
“It may be tempting to attribute the exceptional Storm Eowyn to climate change. However, in this case, it is not straightforward. The storm has been fuelled by an exceptionally strong jet stream over the North Atlantic. However, the strong jet stream is in turn linked to the circulations over North America which have brought cold temperatures over much of the continent, with a strong gradient of temperature with sea temperatures in the Gulf of Mexico (!) and elsewhere. Whether the circulations bringing the cold air to North American have a climate change component is currently unknown. Some speculate it does, but the evidence is not clear.
“Whilst climate change is relatively simple and straightforward at the global scale, it gets complicated at the regional scale where the effects of CO2 interact with the naturally occurring dynamical patterns of climate variability. Although we have a good understanding of the basic thermodynamics of climate change – how it warms and moistens the atmosphere – our understanding of these dynamical impacts of climate change is much less good.
“It is likely that the thermodynamical effects of climate change have intensified Storm Eowyn somewhat. However, we do not know whether the potentially more important dynamical effects of climate change have exacerbated the storm or not. This is an area of ongoing research where the development of high-resolution climate models is proving vital.”
Declared interests
Prof Suzanne Gray: “No conflicts of interest.”
Dr Nicholas Leach: “I am employed by Climate X, a climate risk analytics start-up, in addition to my role at the University of Oxford.”
Dr Chris White: “No conflicts that would affect this.”
Dr Sarah Kew: “Sarah Kew is employed by KNMI as a civil servant to work on links between extreme weather and climate change, is a leading member of World Weather Attribution initiative, and is also funded by the EU-funded project XAIDA (eXtreme events : Artificial Intelligence for Detection and Attribution, XAIDA.eu: https://xaida.eu/) to connect climate services and stakeholders to scientific advances in climate attribution research.”
Dr Ambrogio Volonté: “No conflicts to declare.”
Dr Jess Neumann: “No conflicts to declare.”
Prof Daniela Schmidt: “No competing interests.”
Prof Tim Palmer: “No interests to declare.”
For all other experts, no reply to our request for DOIs was received.