Cyclone Asna

Context

A deep depression currently situated over Saurashtra and Kachchh regions of Gujarat is expected to intensify into acyclonic storm(Cyclone Asna). Cyclone Asna would be the first cyclone to form in August in theNorth Indian Ocean (NIO) regionsince 1981 and the first in the Arabian Sea since 1976.

What are Cyclones?

• A cyclone is alarge-scale system of airthat rotates around the centre of alow-pressure area
• The cyclone forms around the low-pressure area, called adepression, along a zone of cold and warm air exchange called the ‘eye wall’. The eye is the central and calmest part of the cyclone
• From this eye wall, long, arching cloud and rain systems calledrainbands spiral outwards, which bring alternating periods of intense rain and calm spells during a cyclone.
• The air circulates inward in an:
• anticlockwise direction in the Northern hemisphere
• clockwise in the Southern hemisphere

Worldwide terminology

• Cyclones are given many names in different regions of the world – They are known as:
• Typhoonsin the China Sea and Pacific Ocean
• Hurricanesin the West Indian islands in the Caribbean Sea and Atlantic Ocean
• Tornadosin the Guinea lands of West Africa and southern USA
• Willy-williesin north-western Australia
• Tropical cyclonesin the Indian Ocean