The Fujita Tornado Intensity Scale.

This scale is the classic scale which all tornadoes are placed on in order to identify their intensity.

Most tornadoes in USA fall under the F1 and F2 category. Some mutilate vast areas of up to a mile wide across and 50 miles in length. Those tornadoes would fall under the F4 and F5 category and thankfully are a lot less common.

FACT! An F5 tornado is capable of lifting houses off their foundations and hurling them considerable distances. Luckily, only 1% of tornadoes are F5 tornadoes.

Tornadoes can happen at any time of year but are especially common during spring and early summer. May and June are categorised as the peak months in terms of numbers of tornadoes therefore a tornado chasing holiday should be taken during these months in order to increase chances of seeing one. Out of all twelve months however, April appears to be the deadliest month of all. There has been recorded an average of 27 tornado deaths during this month between 1950 and 1999.

What causes a tornado?

Tornadoes are mostly the result of a giant thunderstorm known as a "supercell". These incredibly powerful storms form when warm moist air along the ground travels rapidly upwards. It then meets cooler, drier air. As the rising warm air cools, the moisture it carries then condenses which in turn forms a massive thundercloud. These thunderclouds can often grow to as much as 50,000 ft in height. Varying winds at different levels of the atmosphere feed the deep rotating updraft (mesocyclone) and cause the formation of the tornado's characteristic funnel shape.

Without research, much of what we know today about tornadoes would still be left uncovered. The more we chase them, the more we will find out what makes them tick.