GS1 – Geography
Recent Event:
A powerful EF3 tornado recently tore through the Clayton area of St. Louis in the United States, causing extensive damage.
What is a Tornado?
Commonly called a twister, a tornado is a violently spinning air column extending from a cumulonimbus cloud to the ground. It appears funnel-shaped, often visible due to condensed water vapor, dust, and flying debris.
Destructive Potential:
Tornadoes can achieve wind speeds of over 480 km/h, ranking among the most destructive natural weather events on Earth.
Types of Tornadoes:
- Supercell Tornadoes: Form within large, rotating thunderstorms; most severe.
- Landspouts: Develop from surface-level convergence zones; generally weaker.
- Waterspouts: Occur over water bodies; frequently observed in tropical climates.
- Non-supercell Tornadoes: Associated with weather phenomena like squall lines or sea breezes.
Measuring Intensity – Enhanced Fujita (EF) Scale:
- EF0: Minor damage; wind speeds of 105–137 km/h
- EF1–EF2: Moderate to considerable damage; winds between 138–217 km/h
- EF3: Severe destruction; winds of 218–266 km/h
- EF4–EF5: Catastrophic damage; speeds over 267 km/h
Detection & Monitoring:
Meteorologists rely on advanced tools like Doppler radar, dual-polarization radar, and simulation models. Drones and storm chasers provide real-time data.
- Tornado Watch: Conditions are favorable.
- Tornado Warning: A tornado is either forming or already occurring.
Formation Process:
Tornadoes form under very specific atmospheric conditions:
- Warm, humid air at ground level rises and meets cooler, drier air aloft.
- This creates instability.
- Wind shear (variations in wind speed/direction) induces horizontal spin.
- Strong updrafts tilt this spinning motion vertically, creating a mesocyclone.
- A rear-flank downdraft intensifies the vortex, which may eventually reach the ground as a tornado.
Note: Not every mesocyclone leads to a tornado, and not all funnel clouds touch down.
Tornado Lifecycle:
- Initiation: Begins with rotation in the parent storm.
- Mature Stage: The funnel reaches the surface; most destructive phase.
- Dissipation: The storm weakens, and the vortex gradually vanishes.
Global Tornado Hotspots:
- USA: Most active region globally, especially in “Tornado Alley” (Texas, Oklahoma, Kansas, Nebraska) where warm Gulf air clashes with cold mountain air.
- Bangladesh: Experienced the deadliest recorded tornado in 1989, claiming over 1,300 lives.
- Other countries: Include Canada, Argentina, and Australia.
- India: Tornadoes are rare but have struck states like Bihar (2021) and West Bengal (2020). The Indo-Gangetic plains and parts of Northeast India are relatively more susceptible due to specific meteorological conditions.