What is a tornado?
A tornado is a naturally occurring severe weather condition. It is characterized by a funnel shaped cloud extending from a cumulus cloud or cloud band towards the ground. The base of a tornado is often encircled by a cloud of dust and debris. Most tornadoes do not last very long and are not very strong. There wind speeds can range from less than 100 miles per hour (177 km/h) to more than 300 mph (480 km/h). Tornadoes also range in size from small tornadoes that are approximately 250 feet (80 meters) across to extremely large storms that can be more than 2 miles (3 km) across. Larger tornadoes are more likely to have contact with the ground for longer periods of time and are thus more destructive than smaller storms. Tornadoes have been sighted on every continent of the world except for Antarctica. Tornado alley in the U.S.A hosts the most tornadoes each year.
How is a Tornado Formed?
For a tornado to form the right mix of weather conditions must be present. There needs to be both warm air (which feeds the tornado) and cold air (which cause downdraft to form the tornado) in an area to cause the spiraling air column. Most tornadoes appear out of large thunderstorms called super cells. These super cells draw warm, humid air up in a column or updraft. The formation of a tornado begins when two winds at different altitudes move at different speeds and create wind shear. This causes the air in between the wind to rotate in a horizontal position. The updraft created by the thunderstorm draws the horizontally spinning vortex up into the cloud causing the rotating air to become vertical. There now exists a rotating vortex within the thunderstorm super cell about 2-6 miles wide. It is in this area that most tornadoes form. A low cloud based is formed in the area where the wind is rotating and is commonly known as a wall cloud. The heavy rainfall within the thunderstorm super cell drags a quickly descending area of air known as the rear flank downdraft down towards the ground. This causes the rotating vortex inside the cloud to be dragged down towards the ground also. Whether this will develop into a tornado or not is still very hard to predict and this is the reason why tornadoes are constantly being studied. Scientists think this combination of weather conditions could be the cause of tornadoes.