Tornados are violent, spinning wind storms which are funnel shaped with a narrow base. Tornados are extremely destructive. Although nearly always visible upon formation, they are somewhat shrouded until the moment of release. While they have been recorded throughout the world, the region with the greatest number of tornados runs through the American Midwest and South. Although the United States has the greatest number of instances, the United Kingdom is documented as the most susceptible country to tornados proportional to land area.
Tornados form from a special type of thunderstorm known as a super-cell thunderstorm, though they are also found within squall markings and hurricanes. Tornados are not yet fully understood, but the current models show them being formed when a burst of cool air supersedes a layer of warm air forcing the warm air to quickly rise. So, when thunderstorms develop, this rise of air, results in an increase in wind speed, generally in addition to wind shear, creating a horizontally based, rotating area of air. The internal updrafts of the thunderstorm works like a suction and draws up this area of rotation from a horizontal to a vertical alignment. If this rotation intensifies, a funnel cloud could develop into a situation where the water vapor of the cloud is drawn, or pushed down towards the ground. When the funnel cloud follows the intensity of the vortex towards the ground level is the stage known as "touching down" which indicates the formation of a tornado. Sometimes, however, this is indicator can be misleading, as tornados can have a partial funnel cloud or be wholly invisible. It is not a rarity to find tornados suddenly becoming visible as they move through the air, accruing debris from the land it crosses through.
Although, in regards to the number of incidents the United States has a higher count, the United Kingdom is documented as the most susceptible country to tornados proportional to land area.
Tornados are slightly different depending on geographic locations. Tornados in the northern hemisphere rotate in a counter clockwise, cyclonic direction as warmer air thunderstorms form in sweeping belts from the north, while the jet streams originate from the west, while tornados in the southern hemisphere rotate in a clockwise direction. Oddities are known to occur though, with one in about every 150 tornados in the northern hemisphere being a clockwise rotating storm. Like their differing spin patterns, no two tornados are ever the same- this also holds true for degree of intensity and behavior. And while some tornados have been known to strike the same geographic path, the likelihood of precisely forecasting the place and time of a tornado strike is very low.
Tornados are classified in terms of intensity through the Fujita-Pearson Tornado Scale. Intensity is defined through either data from a high resolution doppler radar or empirical structural damage. The Fujita scale ranges from F0 to F5, with F0 showing minimal damage and F5 showing incredible devastation.