Tornadoes (Twisters)

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:

1. Supercell Tornadoes: Form within large, rotating thunderstorms; most severe.
2. Landspouts: Develop from surface-level convergence zones; generally weaker.
3. Waterspouts: Occur over water bodies; frequently observed in tropical climates.
4. 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:

1. Initiation: Begins with rotation in the parent storm.
2. Mature Stage: The funnel reaches the surface; most destructive phase.
3. 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.