Tornadoes are funnel-shaped vortex clouds protruding from the bottom of cumulonimbus clouds. When a tornado reaches the ground, it will cause a strong whirlwind, which is called a tornado. Tornadoes sometimes hang in the air and sometimes extend to the ground. What appears on the land is called a tornado, and what appears on the sea is called a tornado.

The horizontal scale of tornadoes is very small, the diameter of the surface layer is usually several meters to several hundred meters, and the diameter in the air can reach 3-4 km, even 10km. The vertical range is between 3- 15 km. The survival time is several minutes to dozens of minutes.

Tornado is a small vortex with strong rotation, and the central air pressure is very low, generally lower than several hundred pa around the same height. The ground pressure near the tornado center can be reduced to below 400 hectopascals, and in extreme cases it can reach 200 hectopascals. Due to the low central air pressure and large air pressure gradient, strong wind speed and rising speed are triggered. It is estimated that the wind speed near the tornado center can reach tens to hundreds of meters per second, and in extreme cases, it can reach more than 150 meters per second, and the maximum rising speed can reach tens to hundreds of meters per second. The sharp drop of central air pressure causes the rapid condensation of water vapor, forming a funnel-shaped cloud column. This extremely strong ascending and horizontal airflow is extremely destructive, which can destroy buildings and drag thousands of tons and tens of thousands of tons of heavy objects into the air.

There is a downward airflow near the center of the tornado. From the center to the outside, there is a strong updraft, forming a funnel-shaped cloud surrounded by water or dust. The axis of funnel-shaped clouds is generally vertical, and may tilt or bend when there is vertical wind shear. Tornadoes usually appear alone, but sometimes in pairs. However, pairs of tornadoes often rotate in opposite directions, one is a cyclone and the other is an anticyclone.

Globally, tornadoes mainly occur in mid-latitude (20-50) areas. The United States is the country with the largest number of tornadoes, with an average of about 500 times a year. Australia and Japan are close behind. China has also appeared, mainly in South China and East China. Mostly in spring and early summer.

Tornadoes are formed in a very unstable atmosphere, and their formation mechanism has not been fully explained so far. One view is that the formation of tornadoes is related to the strong updraft in cumulonimbus clouds. Another view is that tornadoes are formed at the intersection of two squall lines.