What causes a hurricane and have we had one in the UK?

Hurricanes form over warm water. Credit: AP/NASA

As we saw a year ago in the Bahamas with Dorian, hurricanes are a powerful force of nature that can leave entire communities homeless and fighting for their lives.

Punishing winds and heavy rain flooded airports, destroyed or severely damaged thousands of homes, crippled hospitals and trapped people in attics.

At least 50 died in Dorian, with the United Nations reporting 61 lost their lives.

Now, a year later, Hurricane Laura is pounding the Gulf Coast of the US with ferocious winds at 150mph.

Meteorologists and authorities can see a storm coming days in advance and, while there is no way of preventing the oncoming onslaught, preparations can be made to save lives and alleviate some of the impact.

So how can we spot a hurricane about to form and what causes them?

What is a hurricane?

A hurricane is the most dangerous storm on Earth. Credit: Alexander Gerst/ESA/NASA via AP

Hurricanes are the most violent storms on the planet.

A hurricane is a huge rotating storm with winds that form over warm waters in tropical areas. They must have winds of at least 74 miles per hour.

The whole storm system may be five to six miles high and 300 to 400 miles wide, according to the Met Office, although sometimes can be even bigger.

They typically move forward at speeds of 10-15 mph, but can travel as fast as 40 mph.

What causes hurricanes?

The categories of hurricane range from 1-5. Credit: PA Graphics

Warm and moist air over the ocean rises from near the surface and is replaced by cooler air. That’s because the air rising leaves a space of low air pressure, which is filled by surrounding air.

This new air becomes warm – as it is near the surface of warm water - and moist and then rises too.

With the warm air rising, the surrounding air swirls in to take its place and this process continues as long as there is enough warm water.

As the warmed, moist air rises and cools off, the water in the air turns into clouds.

As the Earth spins, so too does the whole system of clouds and wind, which is fed by the ocean's heat and water evaporating from the surface.

What is the eye of the storm?

The eye is calm but don't be fooled. Credit: NASA/AP

The famous ‘eye’ of the hurricane forms as the winds continue to spin and can be as wide as 30-65 kilometres.

Despite lying at the heart of the hurricane, it’s by far the most calm part of the storm and is where you’ll find the lowest air pressure.

That’s because the new air rising from the surface doesn’t reach the centre of the hurricane thanks to what is known as the Coriolis effect – which dictates air sucked towards the eye is deflected.

But don’t let that fool you, covering the eye is the eyewall, which is the most dangerous part of the hurricane as that’s where the wind is strongest.

Does climate change affect hurricanes?

As temperatures rise around the world, so too will the sea.

Warmer waters means hurricanes will have more fuel to grow larger and more powerful – that’s because more warm air will rise from the surface of the seas and trigger the potentially deadly process all over again.

Have we ever had a hurricane in the UK?

Strong winds left over from hurricanes have hit the UK. Credit: PA

As they rely on warm water to keep going, the UK is well protected from the strongest hurricanes.

It is possible for the remnants of hurricanes to come near the islands and there have been times when storms have crossed the Atlantic, but they lose a lot of strength.

By the time they’re on or near the UK’s shores, they’re not technically classified as hurricanes anymore as the winds no longer reach speeds of at least 74 mph.

Joan Rix tries to make a call from a destroyed phone box after The Great Storm of 1987. Credit: PA

The Great Storm of 1987 was an exception, bringing gusts up to 100mph to parts of the UK and killing 18.

Though technically not a hurricane – as it did not form in the tropics – the storm did pound the UK with hurricane-force winds.

It was the day before this storm when TV weather presenter Michael Fish became famous for telling viewers the storm would not strike (although he was referring to a separate storm that didn’t reach Britain).

What is the worst hurricane on record?

New Orleans was devastated in 2005. Credit: AP

The Great Hurricane of 1780 hit Puerto Rico, Bermuda and possibly parts of eastern Florida, killing between 22,000 and 27,501.

This storm was well before official records were kept but it is believed this was a Category 5 hurricane – the most extreme level.

In recent times, Hurricane Katrina killed 1,833 in August 2005 in New Orleans, Louisiana.

This was also the most expensive hurricane on record, costing $125 million in repairs.

What’s the difference between a hurricane and a cyclone or typhoonAll three of these terms mean the same thing – the name only changes according to where it formed.

‘Hurricane’ is usually restricted to the Atlantic and north-east Pacific region. In the north-west Pacific they are known as 'typhoons' and elsewhere simply as 'cyclones'.

If sustained wind speeds are between 39 mph and 73 mph they are known as a 'tropical storms'. Once it hits 74 mph, they become one of the three terms.