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A great whirlwind you can either call a storm or simply a low-pressure-area. It comes into being by temperature contrasts between the relative warm air of the sea and an arctic coldfront which built up into a cyclone.
The tropic whirlwinds which rage in the Carribean Sea and at the Gulf of Mexico are called hurricane, precisely said, in the Western Pacific they\'re called tayfun which means \"great wind\" in Chinese, at India they are called \"Willy-Willy\".
Often these storms are several 100 kilometres wide and in the inside they reach up to 400 km/h.
Another kind of whirlwinds are tornados which come to the Northern America every year. In the average 900 whirlwinds are counted in one year. The bad ones demand about 100 or more casualties and cause extensive property damage. At the \"record day\", the 3rd April of 1974, 18 tornados raged within 18 hours, left 315 dead and 5000 injured persons.
Tornados distinguish themselves from the tropic whirlwinds by being built up over the mainland and just to be about 50 kilometres wide but to whirl with a speed of 500 km/h around their own axles.
Such a giantic storm is the result of two big air-masses hitting each other.
The cold and dry winds from the Rocky Mountains stream above the sultry air from the Gulf of Mexico. Warm air spreads and loses weight, because of that it raises up like a balloon and builts up drops of water which comes down to earth as an enormous thundercloud. There are still two conditions which are necessary for a tornado coming into existence. The first one is the sidewind in a big height, which catches the balloon of warm rising air, puts it into a turning movement and forces the warm air, which comes from downside, to circulation.
The second one is that the whirl becomes more and more narrow and faster until a hose is built up. This hose licks warm air from downside and gets more and more temperature and energy. Then it breaks trough the thundercloud and grows - because it wants to lick more warm air - vertical or slanting into the depth.
At the beginning the proboscis is snowwhite because it just exists of fine water drops. But as soon as the proboscis gets in touch with the earth it becomes black because it licks up leaves, dust, branches and things like that and whirls them trough the air with a tremendous force.
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