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There are many different types of storms, most of which are associated with strong winds.
One kind of storm which builds up as a result of atmospheric pressure, is the whirlwind or tornado. A tornado forms where relatively cool air moves over the top of warm, wet air. The changes in wind speed then create a vortex. The air pressure at the centre of the vortex is very low, so when it passes over matter it sucks it up like a vacuum cleaner. The path of a tornado is very narrow. When this is over the sea, water as well as marine life gets pulled into the vortex. As the wind finally collapses, much of what has been sucked up then falls from the sky.
Because tornadoes are so severe it is not always easy for instruments to record the exact wind speed or any other elements of this phenomenon.
Another type of storm is the hurricane, which can begin life as a tropical thunderstorm over warm seas and then extend over a hundred miles in breadth. If the water is warm enough several storms may cluster together, encouraged by strong winds. As the hurricane becomes more concentrated, so the atmospheric pressure within the eye of the storm drops very low. This intense reduction of pressure increases the sea level below the eye, creating huge waves. Torrential rains and huge winds rage as the hurricane moves in a westerly direction. Once the storm reaches land it loses much of its strength, as its environment becomes drier. When a wind reaches 39 mph the National Hurricane Centre names it, allowing us to track the damage it makes.
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