Cyclone landfall
- September 27, 2021
- Posted by: OptimizeIAS Team
- Category: DPN Topics
Cyclone landfall
Subject – Geography
Context: According to the India Meteorological Department (IMD) Cyclone Gulab, the first cyclone post-monsoon, formed in the Bay of Bengal on the evening of September 25, 2021. It may make landfall along the south Odisha and northern Andhra Pradesh coasts by tomorrow evening.
Concept –
What is landfall?
A landfall, in simple words, is the storm moving over the land after its intensification in the ocean (heat source). Therefore, a cyclone is said to make landfall when the centre of the storm (eye) moves across the coast. As per the US National Hurricane Centre definition, it is ‘the intersection of the surface centre of a tropical cyclone with a coastline.’
Tropical cyclones are usually formed in warmer seas. The strongest winds of the cyclone are not at the centre, but at the immediate surroundings of the eye of the storm—usually stronger on one side of the centre. Therefore, very high wind speed can be experienced over the land area when the cyclone is near the land, even when it is yet to make landfall. It can be vice versa too, where the cyclone can make landfall but leave the strongest wind over the ocean.
The landfall usually brings with it high-speed winds, severe storm surge and torrential downpour, all of which can have a severe impact on the region. The storm usually weakens rapidly after landfall as the ocean heat and moisture that fuels the storm is no longer available.
Conditions Favourable for Tropical Cyclone Formation
- 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.
Favorite Grounds for Tropical Cyclones
- South-east Caribbean region where they are called hurricanes.
- Philippines islands, eastern China and Japan where they are called typhoons.
- Bay of Bengal and Arabian Sea where they are called cyclones.
- Around south-east African coast and Madagascar-Mauritius islands.
- North-west Australia.
Nomenclature of Tropical Cyclones
- The naming of tropical cyclones is a recent phenomenon. The process of naming cyclones involves several countries in the region and is done under the aegis of the World Meteorological Organization (WMO).
- For the Indian Ocean region, a formula for naming cyclones was agreed upon in 2004. Eight countries in the region – Bangladesh, India, Maldives, Myanmar, Oman, Pakistan, Sri Lanka and Thailand – all contributed a set of names which are assigned sequentially whenever a cyclonic storm develops.
- Hudhud, Titli, Phethai, Fani, Vayu , Amphan and Nivar are among the names of cyclones in the Indian Ocean region.
Worldwide Terminology of Tropical Cyclones
- They are given many names in different regions of the world – eg. they are known as Typhoons in the China Sea and Pacific Ocean; Hurricanes in the West Indian islands in the Caribbean Sea and Atlantic Ocean; Tornados in the Guinea lands of West Africa and southern USA.; Willy-willies in north-western Australia and Tropical Cyclones in the Indian Ocean.