1. Introduction
A tornado is an intense atmospheric vortex in contact with the ground and the base of a cumulonimbus cloud. Its spiral structure is one of the most spectacular manifestations of atmospheric fluid dynamics. The most intense tornadoes can reach wind speeds exceeding 500 km/h.
2. Tornado Formation
The most violent tornadoes form in supercells — organized rotating thunderstorms. Rotation begins in the storm's mesosphere, several kilometers up, when wind shear (variation of speed and direction with altitude) generates horizontal rotation that is then tilted to vertical by the storm's updrafts. This rotation progressively descends to the ground.
3. Internal Structure of a Tornado
A mature tornado has a Burgers vortex structure: a central core in quasi-solid rotation surrounded by a potential-flow region. The pressure at the center is 10 to 20% below ambient pressure, sucking air and debris upward. The most intense tornadoes can have multiple secondary vortices orbiting around the main vortex.
4. Enhanced Fujita Scale (EF)
- EF0: 105-137 km/h, light damage
- EF1: 138-177 km/h, moderate damage
- EF2: 178-217 km/h, considerable damage
- EF3: 218-266 km/h, severe damage
- EF4: 267-322 km/h, devastating damage
- EF5: >322 km/h, incredible damage
5. Conclusion
A tornado is an atmospheric vortex whose spiral structure results from conservation of angular momentum in a converging fluid. Its formation requires very specific atmospheric conditions — wind shear, convective instability, humidity — which explains why intense tornadoes are concentrated in certain geographic regions.