Wednesday, August 06, 2014, 16:20 GMT – The Weather Network

Tropical storms and hurricanes develop over the warm waters of the tropical Atlantic, usually between the months of June and November, when sea surface temperatures are at their highest.

Most of the systems then track eastwards towards the Caribbean and North America and usually either lose strength when they make landfall or travel over cooler waters.

However, their track occasionally takes them further north and if they interact with the jet stream, they can then be transported towards north-west Europe.

It is virtually impossible for tropical storms and hurricanes to make it to the UK, as the waters around the country are far too cool to sustain them. Instead, the remnants of such systems can occasionally develop into powerful extra-tropical storms.

While such storms are by no means as intense as a hurricane, they can still bring heavy rain and strong winds to the UK, as they still contain some of the vast energy and moisture that they have picked up over the tropical seas.

On average, an ex-hurricane can make its way to the UK every couple of years, often during the late summer and early Autumn when the Atlantic hurricane season is at its peak.

Most will just bring fairly typical unsettled conditions, but sometimes they can interact with the jet stream to develop into powerful storms, bringing torrential rain and strong winds.

We take a look at the top five ex-hurricanes to the hit the UK in recent years.

1. Charley (August 1986)

Charley is probably the most notable ex-hurricane to hit the UK in the last 60 years. Charley developed in the Gulf of Mexico before tracking across Florida and up the east coast of the Unites States, bringing tidal flooding and high winds to the Carolinas and Virginia. As the system moved north-east out of the tropics, it developed into a deep low pressure system as it raced across the Atlantic towards the British Isles.

Wind gusts in excess of 60mph were reported across Ireland and western England and Wales, but it was the heavy and persistent rain that caused the most disruption. Many 6, 12 and 24 hour rainfall records were broken with some locations seeing over 100mm of rain from the storm. Widespread flooding occurred in western areas of the country, particularly in Gloucestershire and Cumbria.

2. Debbie (September 1961)

This storm is probably the most intense ex-hurricane to hit the UK and Ireland in recent times. Debbie developed close to the Cape Verde Islands before reaching strong category 3 hurricane in the central North Atlantic. The storm only slowly weakened as it picked up pace and move up from the south-west to hit Ireland and the rest of the British Isles on 16 September.

Debbie was very rare in the fact that the US National Hurricane centre still classed the system as a category 1 hurricane as it hit the coast of south-west Ireland. However, due to the lack of observational data back in the early 1960s, there is some uncertainty about this.

Wind gusts in excess of 100mph were widely reported across Ireland and western Britain. The strongest reported gust was 113mph at Malin Head in the far north of the island. Hundreds of buildings and homes were completely destroyed in Ireland with hundreds of thousands of trees uprooted. Six people in Northern Ireland were killed due to falling tress.

3. Lili (October 1996)

Hurricane Lili swept through Cuba and the Bahamas in October 1996, before tracking north-eastwards across the Atlantic Ocean. The extra-tropical remants of the storm reached the shores of Britain on 28 October. Southern England and south Wales bore the brunt and it was thought to be the worst storm to hit the region since the Great Storm of 1987. Thousands of homes lost power and six people died due to fallen trees. A storm tide in the Thames Estuary brought some limited flooding.

The storm brought much needed rain to southern Britain as that year’s summer had only seen around 50% of its usual rain in some areas.

4. Gordon (September 2006)

Hurricane Gordon developed into a hurricane in the central North Atlantic without making landfall. However, the remnants of the systems tracked north-eastwards towards the UK to bring strong winds and rain to western areas. High winds in Northern Ireland left over 100,000 people without power.

However, the greatest impact of the storm was actually a late summer heatwave. Hurricanes can pump moist and very warm air north and Gordon did exactly that, with a surge of hot, humid air that pushed north across north-west Europe. This followed a record-breaking hot summer in which July was the warmest month on record over much of the UK.

5. Katia (September 2011)

This was the last ex-hurricane to impact the UK and had a fairly similar track to that of the current storm Bertha, although it steered clear of the Caribbean.

Gusts in excess of 70mph led to huge waves battering the west coast and over £100 million worth of damage was estimated to have occurred. The storm led to the cancellation of the second leg of that year’s Tour of Britain cycle race in north-west England.

Forecast for ex-hurricane Bertha

In terms of Bertha, there is still some uncertainty in whether it will make it to the UK this weekend. Some weather model forecasts don’t develop the system too much, taking it into France or northern Spain, where nothing more than some heavy rain can be expected.

However, some other forecast models still develop the remnants of Bertha into a deep area of low pressure that could bring heavy rain and strong winds to the UK on Sunday. We will be keeping an eye on Bertha over the next few days here at The Weather Network and will have more in our Weekend Weather article tomorrow.