Tropical Cyclone and Storm surges : Basic facts and Prediction | Mrs Sunitha Devi, IMD |

Of India's 7,500 kilometer coastline, almost 5,700 kilometers are highly vulnerable to the impacts of tropical cyclones and related hydro-meteorological hazards and consequently to recurrent loss of life and properties. It is now well recognized that by taking long and short term mitigation measures, the loss of life and properties can be minimized. Though the frequency of Tropical Cyclones (TCs) in the NIO covering the Bay of Bengal and the Arabian Sea is the least in the world (7% of the global total), their impact on the east coast of India as well as the Bangladesh coast is relatively more devastating. This is evident from the fact that in the last 270 years, 21 of the 23 major cyclones (with a loss of about 10,000 lives or more) worldwide occurred over the area surrounding the Indian subcontinent (India and Bangladesh). This is primarily due to the serious storm tide effect in the area.
Thirteen coastal states and Union Territories (UTs) in the country, encompassing 84 coastal districts, are affected by tropical cyclones. Four states (Tamil Nadu, Andhra Pradesh, Orissa and West Bengal) and one UT (Puducherry) on the east coast and one state (Gujarat) on the west coast are more vulnerable to hazards associated with cyclones. Analysed data for the period 1980-2000 shows that on an average, annually 370 million people are exposed to cyclones in India. Cyclones occur in the month of May-June and October-November, with primary peak in November and secondary peak in May (NDMA). Although cyclones affect the entire coast of India the East Coast is more prone compared to the West Coast. An analysis of the frequencies of cyclones on the East and West coasts of India during 1891-2000 show that nearly 308 cyclones (out of which 103 were severe) affected the East Coast. During the same period 48 tropical cyclones crossed the West Coast, of which 24 were severe cyclonic storms. Out of the cyclones that develop in the Bay of Bengal, over 58 percent approach and cross the East Coast in October and November. Only 25 % of the cyclones that develop over the Arabian Sea approach the West Coast. In the pre-monsoon season, corresponding figures are 25 percent over Arabian sea and 30 percent over Bay of Bengal.

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