A small tornado recently passed through the town of Littlehampton on England’s south coast. Strong winds smashed windows, moved cars and left one person injured.
You might associate tornadoes with the plains of the central US, but they’re surprisingly common in the UK too – albeit smaller and weaker. In fact, my former PhD student Kelsey Mulder found that the UK has about 2.3 tornadoes per year per 10,000 square kilometres. That’s a higher density than the US, which as a whole has just 1.3 per 10,000 square km.
The numbers are higher for American states in “Tornado Alley” such as Oklahoma (3.6) or Kansas (11.2). Nonetheless, a random location in the UK is more likely to experience a tornado than a random location in the US.
The data isn’t perfect, however. Tornadoes cannot be observed by satellites and need to be close to weather radars, which can detect the rotation. Thus, most observations are made by humans who then have to report them to the relevant weather service. “Storm-chasers” follow most tornadoes on the American plains, but underreporting may be an issue elsewhere.
Most tornado research has focused on the US, where forecasting and early-warning systems are advanced. There is considerably less research on UK tornadoes. Over the past 12 years, my research group has tried to address this by shedding light on where and when UK tornadoes occur, what causes the storms that produce them and how we can better predict them.
England has three ‘tornado alleys’
Whereas many tornadoes in the US plains occur within a few weeks during the spring, UK tornadoes can occur throughout the year. The UK’s tornado alley is really three regions, most in southern England: an area south of a line between Reading and London with a maximum near Guildford, locations southwest of Ipswich and a line west and south of Birmingham.
These regions have probabilities of experiencing a tornado within a 100 square km area of somewhere between 3% and 6% per year, meaning they could see one as often as every 15 to 30 years.
These tornadoes aren’t as violent as the more extreme ones in the US, but the damage can still be substantial. In July 2005, a large tornado in Birmingham caused £40 million in damages and injured 39. Fortunately, no one was killed. People have died in the past though, for example a strong tornado in South Wales in 1913 killed three.
Although the Birmingham tornado was the most damaging tornado on that day, two others were recorded across the British Isles. Indeed, around 70% of UK tornado days have at least two reports, and 13% produce three or more.
We refer to such days as tornado outbreaks, with the largest-ever UK tornado outbreak occurring on 23 November 1981, producing 104 tornado reports from Anglesey to Norwich.
What causes tornadoes
We still don’t know exactly why the UK has so many weak tornadoes. We do know that “supercells” – rotating thunderstorms tens of kilometres across – form the largest tornadoes in the US but occur less frequently in the UK. Instead, tornadoes in the UK tend to be formed from lines of storms along cold fronts.
Although millions of dollars have been spent researching supercell thunderstorms in the US, there is an increasing awareness that these linear storms also require investigation on both sides of the Atlantic. Our group has been trying to understand what causes some of these parent storms to begin to rotate and eventually spawn tornadoes.
So far, my former PhD student Ty Buckingham and I have been able to identify certain conditions where the wind direction changes abruptly. In such cases, an instability may develop where small perturbations grow into rotating vortices a kilometre or more across, regularly spaced along the front. Such vortices are thought to be the precursor for tornadoes.
Identifying the conditions for this so-called “horizontal shearing instability” should mean we can better predict when and where the parent storms that produce the tornadoes form. But understanding this instability is not the only answer. Other tornado-producing storms do not appear to be associated with this instability, so we still have more to learn.
The next step is understanding how the tornadoes themselves form. For that, we will need both fortuitous observations of such tornadoes forming close to Met Office radars and powerful computer programs that are able to model the atmosphere down to a scale of tens of meters.
Recent advances in computing and our collaborations with colleagues in engineering may yet reveal the secrets of UK tornadoes.
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We still don't know exactly why the UK has so many weak tornadoes. We do know that “supercells
supercells
A supercell is a thunderstorm characterized by the presence of a mesocyclone, a deep, persistently rotating updraft. Due to this, these storms are sometimes referred to as rotating thunderstorms.
” – rotating thunderstorms tens of kilometres across – form the largest tornadoes in the US but occur less frequently in the UK. Instead, tornadoes in the UK tend to be formed from lines of storms along cold fronts.
DENVER — Violent tornadoes can happen just about everywhere on earth, but there are far more in the United States than anywhere else, thanks to a combination of factors. The Gulf of Mexico frequently supplies the first ingredient, packing the low-level air with ample moisture, which warms over the continent.
Europe as a whole is comparable to the size of the US, but there is a vast difference in number of tornadoes and tornado fatalities. From 2011 to 2020, the US averaged a preliminary total of 1,173 tornadoes per year, and Europe around 256.
There are more twisters per square mile in England than in any other country. And they are most common between Reading and London, with the Thames Valley our very own Tornado Alley. On average England is hit by about 34 tornadoes a year – which works out at 2.2 per 10,000km sq.
Tornadoes are fairly uncommon in the US region of New England. Fewer tornadoes are recorded here than anywhere else east of the Rocky Mountains. However, these deadly and destructive storms do occur; on average, about eight tornadoes are reported in the region each year.
The United States has the most tornadoes of any country. Many of these form in an area of the central United States known as Tornado Alley. This area extends into Canada, particularly the prairie provinces and Ontario.
Tornadoes also need cool, dry air which the U.S. gets from the Rocky Mountains. "The fact that we have the Rocky Mountains and the Gulf of Mexico located where they are, means that it's relatively easy to get the ingredients to come together to make tornadic storms in the middle part of the U.S.," Brooks said.
We still don't know exactly why the UK has so many weak tornadoes. We do know that “supercells” – rotating thunderstorms tens of kilometres across – form the largest tornadoes in the US but occur less frequently in the UK. Instead, tornadoes in the UK tend to be formed from lines of storms along cold fronts.
While tornadoes do not occur as frequently in China as they do in the US, they do happen. A peer-reviewed scientific article from 2015 found that China averages fewer than 100 tornadoes per year, and that at least 1,772 people had died from tornadoes in the country in the 50 years since 1961.
The number of emergency situations caused by storms, hurricanes, tornadoes, or twisters in Russia increased in the latest year observed. There were 27 disasters of that type in the country in 2021, compared to two catastrophes recorded in 2019.
It stretches closer to the ground until it eventually meets with that dust cloud. And then, it touches down. In Oklahoma, known as the tornado capital of the world, winds have previously reached a mind boggling 400 kilometres per hour.
According to the National Institute of Water and Atmospheric Research in New Zealand, tornadoes are relatively rare there. On average, around seven to 10 moderate to strong tornado events are reported in New Zealand every year.
The state with the most number of tornadoes classified as "violent", or F4 and F5, is Kentucky, and the state with the highest average intensity ranking for tornadoes is Alabama.
The number in each state depicts the average annual number of tornadoes based on the 20-year period from 2003 to 2022. The two most active states for tornadoes are Texas, with 124, and Kansas, with 87, in an average year.
Most tornadoes are found in the Great Plains of the central United States – an ideal environment for the formation of severe thunderstorms. In this area, known as Tornado Alley, storms are caused when dry cold air moving south from Canada meets warm moist air traveling north from the Gulf of Mexico.
Most tornadoes are found in the Great Plains of the central United States – an ideal environment for the formation of severe thunderstorms. In this area, known as Tornado Alley, storms are caused when dry cold air moving south from Canada meets warm moist air traveling north from the Gulf of Mexico.
While tornadoes occur in all 50 states and Washington, D.C., several states experience minimal tornadic activity in an average season. These states recorded no tornadoes in 2023: Alaska. Hawaii.
Tornadoes have been recorded in every province and territory in Canada. However, tornadoes occur most frequently in two areas - from southern Alberta across southern Saskatchewan and southern Manitoba to northwestern Ontario, and from southern Ontario across southern Quebec to New Brunswick.
Introduction: My name is Fr. Dewey Fisher, I am a powerful, open, faithful, combative, spotless, faithful, fair person who loves writing and wants to share my knowledge and understanding with you.
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