With the UK storm season currently underway, we asked researchers at the National Centre for Atmospheric Science to explain named storms and the recent stormy weather.
Why are storms named?
In the UK, a storm is given a name when it has the potential to cause disruption or damage as a result of strong winds, heavy rainfall or snow, leading to amber or red weather warnings being issued.
The UK storm season begins at the end of the summer in September and ends in August the following year.
In Europe there are three storm naming groups, and each September there is a new alphabetical list of names issued for the upcoming storm season. In Western Europe the list is created by the Met Office in collaboration with the Irish and Dutch weather services. This coincides with when we expect to experience extreme storms, due to low pressure weather systems that occur in the autumn and winter months.
Storms can impact many countries at once, and to avoid confusion, the UK adopts a storm name if another European weather service has already named it.
Storm Henk, which made landfall in the UK on Tuesday 2 January 2024, marked the quickest arrival of a storm beginning with ‘H’ on record since the UK Met Office started naming storms in 2015.
What causes extreme storms in the UK?
Wind is the movement of air in our atmosphere. Air is forced to move by differences in atmospheric pressure, and the Earth’s rotation means that the wind circulates around areas of lower pressure, known as a cyclone. If there is a greater difference in pressure, this causes stronger winds around the cyclone.
Storms often bring heavy rainfall that may lead to flooding. Storms move moisture around the atmosphere, which forces warm and moist air to rise. Wherever the warm, moist air rises, clouds are formed. The formation of clouds also releases energy which can further intensify the storm.
The UK is renowned for being stormy, but why? The jet stream – a core of strong winds around 8-11 km above the Earth’s surface, blowing from west to east – directs weather systems, such as storms, across the Atlantic to the UK.
Why was autumn 2023 so stormy in the UK?
Since the current naming scheme started in 2015, between 0 – 9 named storms hit the UK by the end of each winter. By early January 2024, there have already been 8 named storms – the most during this period so far.
Numerous factors influence the position of the jet stream, however the El Niño event ongoing in the tropical Pacific region is likely having a strong influence on this season’s storms. El Niño typically results in a stormier autumn and early winter, but a less stormy late winter that features calmer cold spells. So the current stormy spell might not last throughout the rest of winter.
Dr Ben Harvey, Senior Research Scientist at the National Centre for Atmospheric Science and University of Reading.
Will extreme storms become more intense and frequent?
Chance can always play a role since UK weather can vary a lot from year to year. Storms tend to vary naturally in intensity and frequency on an annual basis – this makes identifying trends in storms particularly challenging.
However, links between human-caused global warming and storms should be expected. A warming atmosphere is linked with heavier rainfall, because the air is able to hold more moisture – and leads to clouds containing a greater number of larger raindrops.
As the climate continues to warm, the effect will increase, and storms with heavy rain are expected to become more common. Additionally, the extra release of energy by clouds will likely lead to an increased rate of storms that rapidly intensify and a strengthening of the most extreme storms. But while a warmer world is likely making the most extreme storms more intense, the change in the overall number of storms is more uncertain and remains a subject of ongoing scientific research.
Research suggests that currently a third of all storms with strong surface winds, and nearly half by the end of the century, in the North Atlantic region may be accompanied by powerful sting jets as a result of global warming.
What are sting jets?
“Sting jets are narrow jets of air that accelerate as they descend and that can cause extremely strong and damaging surface winds in a relatively small area of the storm, “ explains Dr Ambrogio Volonté, Senior Research Fellow at the National Centre for Atmospheric Science and University of Reading.
Dr Volonté adds: “They are called sting jets as they descend from the tip of the hooked cloud that gradually wraps around the area of low pressure at the centre of the storm. The presence of a sting jet can make intense storms, with strong surface winds, even more damaging.”
Damaging winds in winter storms are not limited to sting jets as they can be caused by a number of different airstreams, and storms can still be extremely damaging even without the presence of a sting jet. For instance, in February 2022’s Storm Eunice – one of the most damaging storms to hit the UK in recent years – the damaging winds were associated with a sting jet and with several other airstreams.
It’s important that we improve scientific understanding of the effects of a warming climate on extreme storms, so that society can mitigate the impacts.
Dr Emily Grace Norton, Meteorological Instrument Scientist at the National Centre for Atmospheric Science and University of Manchester.
Dr Emily Grace Norton is a meteorological instrument scientist at the National Centre for Atmospheric Science and University of Manchester, who uses radar wind profilers to measure the structure of the storms as they pass over the UK. The wind data Dr Norton collects is used by European Meteorological weather services to improve weather forecasts. .
Dr Norton explains the impact of damaging storms: “Extreme storms can cause extensive and expensive damage to homes and infrastructure, cause widespread disruption to travel, and can be a risk to life.” It’s important that we improve scientific understanding of the effects of a warming climate on extreme storms, so that society can mitigate the impacts.”