CYCLONE NIVAR

Subject: Geography

Context: The Bay of Bengal will see its second Severe Cyclone of the year, after Super Cyclone Amphan formed in May. It is likely to hit Tamil Nadu coast by midweek.

Concept:

• The depression will intensify into a cyclone. At this stage, the wind speed will range between 70 to 80 km/hr gusting to 90km/hr.
• The cyclone will further gain strength into a Severe Cyclone category (90 to 100 km/hr gusting to 110 km/hr).

Tropical Cyclones

• Tropical cyclones are violent storms that originate over oceans in tropical areas and move over to the coastal areas bringing about large scale destruction caused by violent winds, very heavy rainfall and storm surges.
• Tropical Cyclones are one of the most devastating natural calamities in the world.
• Tropical cyclones originate and intensify over warm tropical oceans. The conditions favourable for the formation and intensification of tropical storms are:
• Large sea surface with temperature higher than 27° C.
• Presence of the Coriolis force.
• 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.

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.