Tornadoes
Why in news :
- Powerful tornadoes that ripped through Mississippi destroying buildings and obliterating at least one town killed almost two dozen people.
About Tornadoes :
- A tornadois a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud.
- It is often referred to as a twister, whirlwindor cyclone.
- Although the word cyclone is used in meteorology to name a weather system with a low-pressure area in the center around which, from an observer looking down toward the surface of the Earth, winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern.
- Tornadoes come in many shapes and sizes, and they are often visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it.
- Most tornadoes have wind speeds less than 180 kilometers per hour (110 miles per hour), are about 80 meters (250 feet) across, and travel several kilometers (a few miles) before dissipating.
- The most extreme tornadoes can attain wind speeds of more than 480 kilometers per hour (300 mph), are more than 3 kilometers (2 mi) in diameter, and stay on the ground for more than 100 km (60 mi).
- Tornadoes occur most frequently in North America (particularly in central and southeastern regions of the United States colloquially known as Tornado Alley; the United States and Canada have by far the most tornadoes of any countries in the world).
Rotation :
- Tornadoes normally rotate cyclonically (when viewed from above, this is counterclockwise in the northern hemisphere and clockwise in the southern).
- While large-scale storms always rotate cyclonically due to the Coriolis effect, thunderstorms and tornadoes are so small that the direct influence of the Coriolis effect is unimportant, as indicated by their large Rossby numbers.
- Supercells and tornadoes rotate cyclonically in numerical simulations even when the Coriolis effect is neglected.
- Low-level mesocyclones and tornadoes owe their rotation to complex processes within the supercell and ambient environment.
Syllabus : Prelims + Mains; GS 1 – Geography
