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What Causes Tornadoes

Abhijit Naik May 4, 2019
On an average, approximately 800 tornadoes are reported from various parts of the United States every year. Knowing what causes tornadoes will be helpful in adding to your knowledge about this interesting attribute of nature.
Tornadoes, also referred to as twisters or thunderstorms, are violent rotating columns of air, that extend from the ground to cumulonimbus clouds. Though these destructive thunderstorms come in various shapes and sizes, the shape most often observed is that of a funnel―broad at the highest point and narrow at the base.

What Causes Tornadoes to Form?

Conditions suitable for the formation of a tornado develop when varying temperatures and humidity come together and form thunderclouds. This refers to the presence of warm and moist condition in the lower atmosphere and cold and dry conditions in the upper atmosphere.
The place where these varying masses of air meet is known as the dry-line. Such conditions, which are suitable for the formation of a tornado, are most often observed just before a low pressure system develops.
Once the ideal conditions occur, the warm air tries to rise in the atmosphere, while the cold air blocks it. This makes the air in between rotate horizontally. In the meanwhile, the land is heated by the Sun, and hence, the air near the ground becomes warm and starts rising.
Continuous fueling by the heat energy from the Sun ensures that the warm air has an upper hand over cold air. As a result of this, the cold air at the top starts sinking and the warm air below starts rising in a spinning motion.
As the amount of warm air increases, the formation gains height and becomes intense. The intensity of these devastating tornadoes is such that they can clear off anything that comes in their path.

The United States Perspective

In the United States, the cooler polar air masses and warm tropical air masses come together to form a tornado. This is caused as the warm, wet winds from the Gulf of Mexico move towards the north, and the cold, dry winds from Canada move towards the south.
Tornadoes caused during the late winter or early spring are fueled by the strong frontal systems which occur in the Central United States and move towards the east. In the High Plains of the United States, thunderstorms are caused when the air in the lower atmosphere is pushed up along the higher terrain.

Facts About Tornadoes

  • Approximately 95 percent of these tornadoes rotate in counter-clockwise direction.
  • On an average, the speed at which these huge columns of air rotate ranges between 40 to 110 mph.
  • The height of the tornado and its speed have a direct relationship; taller the tornado, faster will it rotate.
  • At times, these monsters can grow to a height of 10 miles in the air, and thus, cause wide-spread destruction in the vicinity.
The United States experiences the most number of tornadoes in the world, followed by the Indian subcontinent. Some of the famous tornadoes which have unleashed havoc in the US include the Waco Tornado (1953) and New Richmond Tornado (1899). The destruction caused by these tornadoes in itself can give you a rough idea of how dangerous they can be.