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How does a tornado form?
1 minutes read
Published 06/20/2013
How does a tornado form?
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    A tornado builds up within minutes and, in relation to its brief duration, is more destructive than a hurricane. Topics Online explains how a tornado forms.
    On Monday, 20 May, a one-and-a half kilometre wide tornado tore through the suburbs of Oklahoma City gouging a 30 km long by 2 km wide corridor of destruction out of the landscape. With wind speeds of over 320 kilometres per hour, the tornado has been classified as the most powerful possible, known as an EF-5 on the Enhanced Fujita scale. At local level tornadoes of this strength can wreak far more destruction than a hurricane. And they form suddenly. The people of Oklahoma had only 15 minutes to protect themselves against the approaching tornado. The tornado swept over the ground for over 40 minutes.

    The formation of a spring tornado

    In contrast to hurricanes, which develop from tropical storms over the sea in summer and autumn, these typical spring tornadoes usually develop over flat stretches of land. A region that is particularly threatened by tornadoes is the "Tornado Alley" in the Midwest of the USA, where the state of Oklahoma also lies. Warm and cold air masses collide here and form gigantic thunderstorm clouds, so-called super cells. The infographics below show how a tornado develops from a super cell.

    Meteorological prerequisites

    A tornado builds up within minutes and, in relation to its brief duration, is more destructive than a hurricane. Topics Online explains how a tornado forms. On Monday, 20 May, a one-and-a half kilometre wide tornado tore through the suburbs of Oklahoma City gouging a 30 km long by 2 km wide corridor of destruction out of the landscape.
    © Munich Re
    Very warm and moist air arriving from the Golf of Mexico moves land inwards over the Tornado Alley towards the northwest.
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    Collision of airstreams

    A tornado builds up within minutes and, in relation to its brief duration, is more destructive than a hurricane. Topics Online explains how a tornado forms. On Monday, 20 May, a one-and-a half kilometre wide tornado tore through the suburbs of Oklahoma City gouging a 30 km long by 2 km wide corridor of destruction out of the landscape.
    © Munich Re
    The higher-lying cold-air winds from the northwest slide at high speed over the warm moist air from the south.
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    Formation of the super cell

    A tornado builds up within minutes and, in relation to its brief duration, is more destructive than a hurricane. Topics Online explains how a tornado forms. On Monday, 20 May, a one-and-a half kilometre wide tornado tore through the suburbs of Oklahoma City gouging a 30 km long by 2 km wide corridor of destruction out of the landscape.
    © Munich Re
    Under the influence of the different wind directions and speeds at higher and lower levels of the atmosphere (wind shear), the rising moist, warm air begins to rotate upwards.
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    Tornado formation

    A tornado builds up within minutes and, in relation to its brief duration, is more destructive than a hurricane. Topics Online explains how a tornado forms. On Monday, 20 May, a one-and-a half kilometre wide tornado tore through the suburbs of Oklahoma City gouging a 30 km long by 2 km wide corridor of destruction out of the landscape.
    © Munich Re
    The spinning movement of the air rising inside the mesocyclone creates an area of low pressure directly below.
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    Munich Re Experts

    Jan Eichner
    Senior Consultant and expert on natural hazards, Corporate Underwriting

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