Source: The Hindu
Why in News?
The India Meteorological Department (IMD) has predicted the Cyclone Asani to intensify into a ‘severe cyclone’ over Southeast regions of Bay of Bengal.
The name Cyclone Asani has been given by Sri Lanka. It means 'wrath' in Sinhalese.
Cyclones that Hit India in 2020-21: Tauktae, Yaas, Nisarga, Amphan.
What is the Occurrence of Cyclones in India?
India has a bi-annual cyclone season that occurs between March to May and October to December. But on rare occasions, cyclones do occur in June and September months.
Cyclone Gulab became the third cyclone of the 21st century to make landfall over the east coast in September, after tropical cyclone Daye in 2018 and Pyarr in 2005.
Typically, tropical cyclones in the North Indian Ocean region (Bay of Bengal and Arabian Sea) develop during the pre-monsoon (April to June) and post-monsoon (October to December) periods.
May-June and October-November are known to produce cyclones of severe intensity that affect the Indian coasts.
What is Classification?
The IMD classifies cyclones on the basis of the Maximum Sustained Surface Wind Speed (MSW) they generate.
The cyclones are classified as severe (MSW of 48-63 knots), very severe (MSW of 64-89 knots), extremely severe (MSW of 90-119 knots) and super cyclonic storm (MSW of 120 knots or more). One knot is equal to 1.8 kmph (kilometers per hour).
What are the Tropical Cyclones?
A tropical cyclone is an intense circular storm that originates over warm tropical oceans and is characterized by low atmospheric pressure, high winds, and heavy rain.
A characteristic feature of tropical cyclones is the eye, a central region of clear skies, warm temperatures, and low atmospheric pressure.
Storms of this type are called hurricanes in the North Atlantic and eastern Pacific and typhoons in SouthEast Asia and China. They are called tropical cyclones in the southwest Pacific and Indian Ocean region and Willy-willies in north-western Australia.
Storms rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere.
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.
