A Closer Look at How Do Tornadoes Form

How do Tornadoes Form
One of the most annihilating form of natural calamities, tornadoes, can cause a lot of damage.
ScienceStruck Staff
Last Updated: Jun 20, 2018
Did You Know?
Owing to the vast presence of flat and low-lying topography, the United States has more occurrences of tornado than any other country in the world.
Thunderstorms do not form in restricted geographical locations and same is the case with tornadoes. Tornadoes have been reported to develop in all the continents except Antarctica.
Tornado Sunset
When it comes to US, each and every state has been documented with some of the most intense tornadoes at one point of time. Apart from the US, the countries that are hit by destructive tornadoes are Bangladesh and Argentina.
In spite of this, the basic questions of how exactly a tornado is formed and what triggers its development remain a mystery. Crude ideas and theories have been postulated but none have been officially recognized; the research continues till date.
Formation of a Tornado
Tornado and Lightning Bolt
The most lethal and destructive tornadoes stem from supercell thunderstorms. The supercell thunderstorms are rotating storms having a precise circulation called mesocyclone. Thus, in order to understand the formation of a tornado, one needs to know the development of a mesocyclone.
A mesocyclone is a presence or formation of spinning air within a convective storm. This region of spinning motion (usually within a fluid) is called a vortex. Here, the cyclonic air travels and rotates in a vertical axis.
It forms when the speed of wind -- depending on the height, sets the air spinning in a horizontal manner, called crosswise spin. The updraft (vertical air movement) of the thunderstorm then subjects the air to travel in a vertical mode.
Now, the entire column of the spinning air rotates as a column perpendicular to the surface of the ground, known as streamwise spin. It eventually results into a whirling air column having a weak rotation known as a mesocyclone.
The Dynamic Pipe Effect
Powerful Tornado
The swirling of the column of air continues in the updraft where the rotating motion is responsible for balancing the airflow.
Here, the force that sets the inward movement of the air in the rotating column is balanced and matched by the centrifugal force taking place in the outward direction.
Storm Clouds Forming
Once this equilibrium is achieved, the column of air steadily travels in a circular motion around the axis of the mesocyclone. This state is called the dynamic pipe effect.
The air that travels around the mesocyclone axis is taken via the bottom portion of this dynamic pipe. This results in an agitated rotation at the pipe's bottom and pushing upward of the inflow air entering the pipe. The mesocyclone thus increases in height, further intensifying its rotating speed.
Wall cloud formed during a tornado.
The dynamic pipe effect gives rise to a mesocyclone that extends up to 9 miles above the surface of the ground. The mesocyclone then reduces or lowers in height until right below the base of the cloud where cool air starts to enter.
Black tornado funnel and lightning over field during thunderstor
This cool air then converges with warm air from the updraft. This results in the formation of a wall cloud, which also exhibits a rotating cylindrical nature. Usually, the maturity of the mesocyclone is decided when the wall cloud forms.
Tornado Core
Tornadic Supercell
After mesocyclone is formed, the point where the updraft and downdraft interact, intensified spinning occurs with a rotation strong enough to develop a small dynamic pipe. This pipe is the tornado core, and the parent mesocyclone is now termed as a tornado.
A tornado can either be a supercell or a non-supercell. In a non-supercell tornado, the foremost condition for its formation is that the crosswise spin has to be formed as the first stage. The other essential factor is the presence of a thundercloud. In case of a supercell tornado, the tornado develops from the mesocyclone of a supercell thunderstorm.
Researching and understanding the science behind formation of a tornado is not yet fully developed. Since a tornado does not always travel close to the meteorological instruments, its intensity is often gauged by analyzing the destruction and damage it causes.