The tornado is by far the most destructive and probably the most beautiful aspect to severe weather. Not all torandoes come from the supercell thunderstorm, however most of them do. A tornado is a large rotating column of air extending downward from the base of the thunderstorm to the ground. If this rotating column of air doesn't touch the ground, it is called a funnel cloud. A tornado may last from anywhere from just minutes on the ground to a couple hours. This all depends on how strong the tornado is and what kind of conditions it forms in.
Life cycle of the Tornado
Although not all tornadoes come from supercelled thunderstorms, the larger and stronger ones have been known to come alone with mesocyclones activity. The winds from a mile down inside the supercell thunderstorms produce this horizontal roll of wind. As this roll of wind gets picked up by the updraft, the horizontal roll then becomes more vertically-oriented which allows the mesocyclone to take shape. As all of this is going on, the tornadic circulation begins in the mid levels of the atmosphere (about 20,000 feet). This is where the storm's updraft and mesocyclone are the strongest and this rotation begins to build upward and downward. During this time frame, a downdraft develops on the rare side of the storm at the mid levels. This particular downdraft is called the rear flank downdraft (RFD). The RFD connects with the rotating column in the middle of the storm allowing the tornadic circulaion to begin reaching for the ground on the backside. Baromatric pressures near the ground drops quickly in anticipation of drawing the tornadic circulation and RFD down. After the tornado touches the ground, ample amounts of warm, moist air continue to flow into the tornado/mesocyclone. The RFD will begin to wrap itself around the tornado to begin to cut it off from the main circulation. This might take a while to do because the actual tornado might be extremely large in diameter. When the RFD completely wraps itself around the tornado, the inflow is completely cut off and the tornado will gradually lose its intensity. The actual funnel will begin to decrease in size and the tornado will begin to tilt with height. The tornado will take on a ropelike appearance before it completely disappears. Not all tornadoes go through the life cycle talked about above, some tornadoes go from the developing stage straight to the dissipating stage.
As a tornado moves through its life, it can take on different appearances as it develops, matures, and decays. One of these different looks a tornado can have is a multi-vortex. A multi-vortex tornado has two or more vortices spinning around each other or a common center. Some of the most deadly and most costly tornadoes in the US have been multi-vortex. Another type of shape and appearance for a tornado is the single vortex. This is just one single vortex, extending down from the base of the thunderstorm to the ground. The single vortex tornado is usually not that powerful and most tornadoes recorded in the United States are of these type.
Tornadoes have their own classification scale. This scale was developed by a renowned severe weather researcher, Dr. Theodor Fujita. Dr. Fujita developed a rating scale to base tornadoes by their intensity. His scale, known today as the F scale, gives the strength of a tornado a numerical number ranging from F0 to F5. F0 is the weakest and F5 is the strongest. The F scale is used to identify the tornadoes strength from the damage it occurs on buildings. The Fujita scale provides one of the best guidelines for classifying tornadoes according to their intensities.