Tornadoes are caused by a specific set of atmospheric conditions, primarily involving the collision of warm, moist air with cool, dry air, which leads to the formation of severe thunderstorms known as supercells. These supercells have a rotating updraft called a mesocyclone. Wind shear, which is a change in wind speed and direction with altitude, causes horizontal rotating air tubes that can get tilted vertically by the storm's updraft, forming a rotating funnel cloud. When this funnel cloud touches the ground, it becomes a tornado. This process is fueled by atmospheric instability and the interaction of different air masses, typically occurring in regions and seasons with significant temperature and humidity contrasts.
Key Causes of Tornado Formation
- Warm, moist air near the Earth's surface collides with cool, dry air above.
- Strong wind shear causes rotation in the air.
- Atmospheric instability causes warm air to rise quickly through cooler layers.
- Formation of supercell thunderstorms with rotating updrafts (mesocyclones).
- The rotating air forms a visible funnel cloud, which becomes a tornado upon touching the ground.
These conditions often happen in places like the central United States ("Tornado Alley") during spring and early summer, when temperature and humidity contrasts are highest.