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Cyclone Fengal made landfall over Puducherry on Saturday (November 30) evening, with strong winds and heavy rains witnessed in parts of Tamil Nadu in recent days. As a result, flight operations were also suspended at Chennai airport till 7 pm Saturday. The Tamil Nadu government has also declared a holiday for all education institutions in the state and IT companies are urged to permit employees to work from home.
Cyclone Fengal is a tropical storm. The National Disaster Management Authority classifies cyclones broadly into two categories: extratropical cyclones and tropical cyclones. Here is what you need to know about them.
A cyclone is a large-scale system of air that rotates around the centre of a low-pressure area. It is usually accompanied by violent storms and bad weather. As per NDMA, a cyclone is characterised by inward spiralling winds that rotate anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
Also known as mid-latitude cyclones, extratropical cyclones occur outside of the tropic. They have “cold air at their core, and derive their energy from the release of potential energy when cold and warm air masses interact”, according to the US National Oceanic and Atmospheric Administration (NOAA). It added that such cyclones always have one or more fronts — a weather system that is the boundary between two different types of air masses. One is represented by warm air and the other by cold air — connected to them, and can occur over land or ocean.
Tropical cyclones are those which develop in the regions between the Tropics of Capricorn and Cancer. They are the most devastating storms on Earth. Such cyclones develop when “thunderstorm activity starts building close to the centre of circulation, and the strongest winds and rain are no longer in a band far from the centre,” NOAA noted.
The core of the storm turns warm, and the cyclone gets most of its energy from the “latent heat” released when water vapour that has evaporated from warm ocean waters condenses into liquid water, the agency added. Moreover, warm fronts or cold fronts aren’t associated with tropical cyclones.
Tropical cyclones have different names depending on their location and strength. For instance, they are known as hurricanes in the Caribbean Sea, the Gulf of Mexico, the North Atlantic Ocean and the eastern and central North Pacific Ocean. In the western North Pacific, they are called typhoons.
