Cyclone, Hurricane, Tornado and Twister are all closely related weather phenomena associated with low-pressure wind systems.

Cyclone and Hurricane:

• A tropical cyclone is a generic term used by meteorologists to describe a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters and has closed, low-level circulation.
• Once a tropical cyclone reaches maximum sustained winds of 74 miles per hour or higher, it is then classified as a hurricane, typhoon, or cyclone depending upon where the storm originates in the world.
• The only difference between a hurricane, a cyclone, and a typhoon is the location where the storm occurs.
• In the Atlantic and Northeast Pacific, the term “hurricane” is used. The same type of disturbance in the Northwest Pacific is called a “typhoon” and “cyclones” occur in the South Pacific and Indian Ocean.
• Tropical cyclones rotate counter-clockwise in the Northern Hemisphere.
• Cyclones are an oceanic phenomenon that fizzles out once they reach land because they lose their source of moisture. They can last for days.
• Hurricanes/typhoons/cyclones are storm systems formed when warm tropical waters release heat as moist air rises, causing condensation of the water vapour in the air. These storm systems are characterized by a low pressure center and if the conditions last, they can result in severe thunderstorms, violent winds, heavy flooding, and devastating waves.

Conditions for formation:

The formation of a cyclone is called Cyclogenesis.

• Large sea surface with temperature higher than 27° C.
• Presence of the Coriolis force enough to create a cyclonic vortex.
• Small variations in the vertical wind speed.
• A pre-existing weak low-pressure area or low-level-cyclonic circulation.
• Upper divergence above the sea level system.

Tornado and Twister:

• Tornado and twister are different names for the same type of storm—a violently rotating column of air over land associated with a severe thunderstorm.
• Tornadoes are usually a downward spiral stemming from a cumulonimbus cloud and are often accompanied by rain, hail, or sleet.
• Tornadoes occur almost exclusively over land.
• Tornadoes range in diameter from metres to hundreds of metres and generally last from a few seconds up to half an hour.
• They have an intense updraught near their centre, capable of lifting heavy objects such as cars and trees and causing enormous damage.

Conditions for formation:

• Instability refers to unusually warm and humid conditions in the lower atmosphere, and possibly cooler than usual conditions in the upper atmosphere.
• Wind shear in this case refers to the wind direction changing, and the wind speed increasing, with height.
• An example would be a southerly wind of 15 mph at the surface, changing to a southwesterly or westerly wind of 50 mph at 5,000 feet altitude.
• Tornadoes form when warm air meets cold air, causing unstable pressures.

Occurrence in India:

Cyclones as well as tornadoes both occur in India.

Cyclones originate in the Bay of Bengal region as well as in the Arabian Sea region. The eastern coast of India is more prone to cyclones than the western coast. Most of the cyclones originate in the Bay of Bengal, hence east coast is vulnerable.

Tornadoes of weak strength occur in north-western and north-eastern region of the country. It mostly affects Bangladesh.

However, unlike cyclones the frequency of tornadoes outbreak is very low.

Conclusion:

 India is prone to cyclones and tornadoes. With increasing global warming, the conditions for formation of cyclones are more favourable. This has lead to increased weather events causing damage to man and material.