By Ajit Tyagi
The author is Koteswaram Professor, Ministry of Earth Sciences, Air Vice Marshal (Retd) and Former Director General of India Meteorological Department.
A tropical cyclone is an intense low pressure system that is classified on the basis of its wind speed. The phenomena has a definitive structure and a well-defined life cycle.
Tropical cyclones (TCs) are intense low pressure systems where the wind speed in the surface circulation system exceeds 33 nautical miles per hour (knots). The low-pressure systems over the northern Indian Ocean (NIO) are classified (Table 1) on the basis of associated maximum sustained surface wind (MSW) at the surface level. Systems with the intensity of depressions and above are considered cyclonic disturbances. TCs occurring over the north Atlantic Ocean are known as hurricanes and those occurring over the Pacific...