Climate of The United Kingdom - Severe Weather

Severe Weather

While the United Kingdom is not particularly noted for extreme weather, it does occur, and conditions have been known to reach extreme levels on occasions. In the winter of 1982, for a few days parts of central and southern England experienced temperatures lower than central Europe and Moscow. In contrast, the summers of 1975 and 1976 experienced temperatures as high as 35 °C (95 °F). It was so dry the country suffered drought and water shortages.

Extended periods of extreme weather, such as the drought of 1975–1976 and the very cold winters of 1946–1947, 1962–1963, 1978–79, 1981–1982, 2009–2010 and 2010–2011, are often caused by blocking anti-cyclones which can persist several days or even weeks. In winter they can bring long periods of cold dry weather and in summer long periods of hot dry weather.

There have also been occurrences of severe flash floods caused by intense rainfall, the most severe was the Lynmouth disaster of 1952 in which 34 people died and 38 houses and buildings were completely destroyed. In the summer of 2004, a severe flash flood devastated the town of Boscastle in Cornwall. However, the worst floods in the United Kingdom in modern times occurred in the North Sea flood of 1953. A powerful storm from the Atlantic moved around Scotland and down the east coast of England. As it moved south it produced a storm surge which was magnified as the North Sea became narrower further south. By the time the storm affected south-east England and the Netherlands, the surge had reached the height of 3.6 metres (12 ft). Over 300 people were killed by the floods in eastern England.

Thunderstorms are most common in southern and eastern England, and least common in the north and west. In London, thunderstorms occur on average 14–19 days a year, while in most of Northern Ireland and the west of Scotland thunderstorms occur on around 3 days a year. Occasionally, thunderstorms can be severe and produce large hailstones as seen in Ottery St Mary, Devon in October 2008, where drifts reached 1.8 metres (5 ft 11 in).

Strong winds occur mainly in the autumn and winter months associated with low pressure systems. The Great Storm of 1987 (23 fatalities) and the Burns' Day storm of 1990 (97 fatalities) are particularly severe examples. The United Kingdom has around 33 tornadoes per year, which is the second highest amount per land area in the world.

The most rain recorded to fall on a single day was 279 mm at Martinstown (Dorset) on 18 July 1955, but also 243 mm fell at Bruton, Somerset on 28 June 1917. Heavy rain also fell between 20 and 25 June in 2007; some areas experienced a months rainfall in one day. Four people died in the flooding and over £1.5 billion of damage to businesses and properties was caused. On 19 August 1993, London Heathrow Airport recorded 257mm of rainfall.

Tropical cyclones themselves do not affect the UK due to the seas being too cold, they need temperatures above 26.5 °C (79.7 °F) to remain active. The waters near the UK, the Atlantic Ocean, only have temperatures of 10 to 15 °C (50 to 59 °F), so any tropical cyclone that does come anywhere near the UK has said to have undergone a process called extratropical transition. This now means it is an extratropical cyclone, which the UK frequently experiences. The Great Storm of 1987 was a very deep depression which formed in the Bay of Biscay, which also contained the remnants of Hurricane Floyd. Hurricane Lili of 1996 and Hurricane Gordon of 2006 both crossed the UK as strong extratropical cyclones with tropical storm-force winds, causing transport closures, power-cuts and flooding in Northern Ireland, Scotland and South West England. In 2011, the remnants of Hurricane Katia passed over northwestern Scotland with winds near 70 mph (110 km/h).