Tornadoes happen when warm and cool airstream's collide, creating a rotating area of low atmospheric pressure. Air within a low pressure front has a natural tendency to rise and creates a strong upward draught. This draws in surrounding warm air from ground level, causing it to spin faster and faster.In order for a vortex – a spiralling funnel of wind – to be classified as a tornado, it must be in contact with both the ground below and the storm cloud above. A tornado’s path is rarely more than 250m across, but can be as much as one mile wide.
There are 5 categories of Tornado, these categorise and scaled by the force and power of destruction combined with the speed of the winds within the vortex.
The intensity of a tornado is determined by the Fujita scale:
F1 Tornado - wind speeds between 73-112mph. Even the smallest tornadoes can peel slates from roofs and drive moving cars off the road.
F2 Tornado - wind speeds between 113-157mph. Roofs of some houses will begin to lift off and mobile homes in the tornado’s path would be demolished.
F3 Tornado - wind speeds between 158-207mph. Heavy trees will be uprooted and walls and roofs of solid buildings will be torn away like matchsticks.
F4 Tornado - wind speeds between 208-260mph. Locomotive engines and 40 tonne articulated trucks will be flung around like toys.
F2 Tornado - wind speeds between 113-157mph. Roofs of some houses will begin to lift off and mobile homes in the tornado’s path would be demolished.
F3 Tornado - wind speeds between 158-207mph. Heavy trees will be uprooted and walls and roofs of solid buildings will be torn away like matchsticks.
F4 Tornado - wind speeds between 208-260mph. Locomotive engines and 40 tonne articulated trucks will be flung around like toys.
F5 Tornado - wind speeds between 261-318mph. Cars are flung like stones for hundreds of metres and entire buildings can be ripped from the ground. The force is similar to that of an atomic bomb.
Predicting Tornadoes
Even though technology has improved vastly in weather prediction, it is still impossible to predict when a tornado is going to touch down. Meteorologists observe changes and development of air temperature, pressure and wind patterns. Atmospheric shifts within these elements can lead to 'tornadic' thunderstorms, however it is still far from possible to predict two days in advanced, it still relays on guess work.
The word or name Tornado derived from the Spanish word for thunderstorms, Tronada. A tornado is often is refered to a twister or a cyclone. The Glossary of Meteorology defines a tornado as "a violently rotating column of air, in contact with the ground."
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