Tornado: How the spiralling vortex is formed
Saturday 30 July 2005
Tornadoes form during thunderstorms when warm, humid air collides with colder air to form a swirling vortex that extends down from the clouds and sometimes reaches the ground where it can cause extensive damage.
Warmer air rises rapidly above colder air, forming an updraft that begins to move in a swirling motion and reaches along the length of the column to cause the classic spinning, or twisting.
Just as water leaves a bath more efficiently by spinning down the plughole, so warm, humid air rises more effectively through a storm cloud by twisting in the vortex.
The downward moving column of air in a tornado - the funnel cloud - is caused as water vapour condenses into its outer sheath because of falling pressure and temperature. Eventually, the funnel can reach the ground and, with it, comes the high-speed winds created by the sudden clash of warm and cold air.
Yesterday's tornado in Birmingham, which had winds of up to 130mph, was small by global standards. In America bigger tornadoes with wind speeds of nearly 200mph are regular.
Nick Grahame, chief forecaster at the Meteorological Office in Exeter, said Britain experiences about 33 tornadoes on average a year but it can depend on the number of summer storms.
In 2003, there were just nine tornadoes reported to the Met Office, whereas in 1981 there were 156.
Dolphins ‘deliberately get high’ on puffer fish nerve toxins by carefully chewing and passing them around
The big thaw: Greenland ice cover is melting away
The climate change paradox: Rainforests are being felled... but the world is getting greener
Climate change: Six major energy companies write to United Nations to request help in setting up carbon pricing scheme
Pester power: The new weapon in the fight against global warming
- 1 School kitchen manager 'fired from Colorado school for giving hungry students free lunches'
- 2 California man brutally beat 82-year-old Sikh grandfather he mistook for 'one of those people'
- 3 Amber Peat: Body found in search for missing 13-year-old who ran away after argument with her parents
- 4 Gay teenager 'forced to have sex with his own mother' to 'cure' his homosexuality, campaigners in India say
- 5 Charles Kennedy 'had better judgement drunk than many sober politicians' says Ian Hislop
Thousands of teenage girls enduring debilitating illnesses after routine school cancer vaccination
Migrants in Kos: Photos show real tragedy after Brits abroad complain of 'awkward' holidays
British tourists complain that impoverished boat migrants are making holidays 'awkward' in Kos
Michael Gove determined to scrap the Human Rights Act – even if Scotland retains it
Threat to scrap Human Rights Act could see UK follow Nazi example, warns UN official
Church of England 'one generation away from extinction' after dramatic loss of followers
Competitive salary & benefits: MBDA UK Ltd: Whats the opportunity? A pro-act...
Competitive salary & benefits: MBDA UK Ltd: Whats the opportunity? The small...
£25000 - £35000 per annum: Recruitment Genius: Fabricator welder required for ...
£14564 - £15311 per annum: Recruitment Genius: Inbound Customer Service Adviso...