Cyclones AND Depressions

A very significant feature of the climatic pattern of the coastal areas is its proneness to cyclones and depressions. Popularly known as 'Toofan' the tropical cyclone picks up energy from the warm waters of the ocean and develops into a destructive intensity, ravaging human settlements and vegetation as it crosses the coast. Cyclones are the most dynamic and energetic of all natural phenomena in their capacity to destroy and devastate, comparable perhaps only to earthquakes. The maximum wind speeds during cyclones can be as high as 300 kmph.

Cyclones originate in low-pressure areas in the south Bay of Bengal. Presence of certain objective conditions such as sufficiently large ocean areas with temperatures above 260 centigrade, presence of a weak vertical wind sheer in the basic current, large cyclonic vorticity, high middle level humidity etc. making a low pressure area intensify into becoming a depression, and winds reaching a gale turn into a squall, developing the potential to intensify into a cyclonic storm.

Whenever a cyclone has a sufficiently long travel over the ocean, it picks up further energy from the sea surface, increasing its capability to intensify rapidly into a severe cyclone to cause torrential rains and furious winds. At the time when the cyclone crosses the coast, the sea is almost lifted surging forward and this is called a Storm Surge.

Storm surges cause high tidal waves of more than three to four meters, inundating inland areas upto 20 kms. It is this kind of flash flooding caused by storm surges or tidal waves that are normally responsible for most of the damages, particularly in terms of human life. Cyclones normally occur on the east coast during the months of May and November during the south west and north east monsoons.