A tornado deploys exceptional destructive power, surpassing that of a tropical cyclone per square meter.
Some tornadoes generated the most violent winds ever recorded on the surface of the globe.
Each year, this fearsome atmospheric whirlwind results in the deaths of 300 to 400 people, with nearly half of these tragedies occurring in the United States, according to estimates from the World Meteorological Organization.
The tornado, a destructive weather phenomenon
The tornado is an atmospheric disturbance of great intensity but of restricted dimensions, characterized by violent winds.
It is distinguished from hurricanes by its limited size.
Considered the most violent and destructive meteorological phenomenon, it can generate gusts exceeding 300 km/h, or even reaching more than 700 km/h in extreme situations.
Despite this impressive power, the tornado is characterized by a relatively limited geographic extent and lifespan.
A funnel-shaped structure
Tornadoes, violent and destructive whirlwinds of rotating winds, have several distinctive characteristics that differentiate them from other weather phenomena.
The most iconic visual characteristic of a tornado is its funnel shape.
This rotating structure descends from the storm cloud, eventually touching the ground.
However, not all tornadoes necessarily have a visible funnel shape, particularly if they are obscured by rain or dust.
Tornado in the United States in the state of Minnesota.
Istock / Chad Cowan
These meteorological phenomena are characterized by a violent rotation of the air.
This rotation can occur at different altitudes but rotation at ground level is the most destructive.
Swirling winds can reach extremely high speeds constituting a major destructive force.
Tornadoes generally move quickly across the landscape.
Their speed of movement can vary but they cover several kilometers in a short time.
This rapid movement sometimes makes them difficult to follow and increases the difficulty of warnings and evacuations.
The Fujita scale for measuring tornado intensity
The lifespan of a tornado can vary greatly.
Some tornadoes are short-lived, touching down for only a few minutes, while others persist for an hour or more.
The duration depends on various factors including weather and topographical conditions.
Tornadoes typically form against the backdrop of supercell thunderstorms which are extremely powerful storms.
Conditions conducive to the formation of tornadoes include the meeting of warm and cold air masses, atmospheric instability and the presence of winds aloft.
Meteorologists use the Fujita Scale (EF) to classify the intensity of tornadoes based on the damage they cause.
The scale goes from EF0 (least intense tornado) to EF5 (most intense tornado).
Property and structural damage are assessed to determine the strength of the tornado.
Tornadoes are accompanied by other dangerous weather phenomena, such as heavy rain, hail and lightning.
These elements increase safety risks and contribute to the devastating effects of a tornado.
What are the favorable conditions for the formation of tornadoes?
The formation of tornadoes is associated with specific weather conditions.
Collision of warm and cold air masses
The collision of hot and cold air masses
is a key element.
When a warm, humid air mass collides with a cold, dry air mass, it creates atmospheric instability that is conducive to the formation of tornadoes.
Atmospheric instability results from the presence of warm air at the surface and colder air aloft.
This disparity creates an environment conducive to convection, where warm air rises quickly, encouraging air rotation.
Weather fronts
Weather fronts, especially cold fronts, provide the temperature difference necessary to create favorable conditions for air rotation and tornado formation.
The presence of winds aloft, particularly winds changing direction and speed with altitude, is crucial.
This creates wind shear, promoting horizontal rotation of the air.
Supercellular conditions
Tornadoes most often form within supercell thunderstorms, which are storms characterized by sustained rotation within the cloud.
Supercell conditions provide an environment conducive to the formation and maintenance of tornadoes.
Topography
Topography can influence the formation of tornadoes.
For example, the presence of hills or mountains can modify wind circulation and create conditions conducive to rotation.
Humidity
Sufficient humidity in the lower layers of the atmosphere is important.
Moist air contributes to instability and convection, providing the energy for tornadoes to form.
What is the life cycle of a tornado?
The life cycle of a tornado can be divided into several distinct stages, although there can be variations and nuances depending on specific weather conditions.
They generally form under specific weather conditions, often within powerful supercell thunderstorms.
Factors such as the meeting of warm and cold air masses, atmospheric instability and the presence of winds at altitude favor the formation of a rotation in the atmosphere.
The initial rotation strengthens as the updraft inside the thundercloud becomes more powerful.
A rotating column of air begins to descend from the cloud, forming a funnel structure.
At this point, the tornado is fully developed and reaching its maximum size.
The rotating column of air touches the ground, forming a visible funnel.
Tornado winds are strongest during this phase, potentially causing significant damage.
Weather conditions change, weakening the updraft that powers the tornado.
The tornado begins to weaken, and the rotating column of air rises toward the thundercloud.
The tornado becomes less visible and eventually dissipates completely.
What are the devastating effects of tornadoes?
Tornadoes have devastating effects on the regions they touch.
The extremely strong winds associated with tornadoes destroy buildings, tear off roofs, and demolish light structures.
Homes, schools and other infrastructure may be destroyed.
Violent winds uproot trees, uproot plants and destroy vegetation in their path.
This can cause additional hazards such as falling trees or flying debris.
A devastated house after a tornado struck Mississippi in March 2023. REUTERS/Cheney Orr
Heavy rains sometimes associated with tornadoes result in flooding that causes additional property damage and poses a safety risk.
Tornadoes generate dangerous debris that is thrown at high speed through the air: pieces of wood, pieces of metal, broken windows and other debris become projectiles, representing a danger to people and property.
Tornadoes can cause fatalities due to direct damage to structures and the hazards associated with flying debris.
Strong winds also cause serious injuries.
Economic costs
associated with material damage, reconstruction, agricultural losses, can be considerable.
People affected by tornadoes are forced to leave their homes due to property damage or safety hazards.
Tornado Preparedness and Risk Management
Tornado preparedness and risk management are essential to reducing the devastating consequences of these severe weather events.
Setting up early warning systems to inform the population of the imminent approach of a tornado can be effective.
This may include the use of sirens, emergency media messages and mobile applications.
The different affected territories are developing and implementing comprehensive emergency plans at the community, school and individual levels.
These plans include evacuation procedures, emergency shelters and means of communication.
Governments can build tornado shelters resistant to strong winds in at-risk areas.
These shelters have the possibility of being underground constructions, bunkers or reinforced rooms in buildings.
To address risks and improve tornado forecasting, many countries are investing in advanced weather technologies.
Doppler radar and other monitoring systems provide crucial data for issuing early warnings.
This process may be accompanied by relief coordination plans involving emergency services, government organizations, civil protection agencies and volunteers.
A rapid and coordinated response is crucial to minimize human and material losses.