Some Characteristics of Translational Speed of Cyclonic Disturbances Over North Indian Ocean in Recent Years

Tropical cyclone (TC) is one of the severe disastrous weather events causing loss of property and life, especially for north Indian Ocean (NIO) basin. According to Mohapatra et al. (Nat Hazards 63:1601–1620, 2012b), entire east and west coast of India is prone for TC activity. However, the degree of proneness varies from district to district depending upon the number of TCs and severe TCs crossing/affecting the district as well as, associated adverse weather like heavy rain, gale wind and storm surge over the district due to the landfalling TCs (Mohapatra et al., Nat Hazards 63:1601–1620, 2012b). About 11 cyclonic disturbances (CDs) with maximum sustained wind speed (MSW of 17 knots or more) including depressions (MSW of 17–33 knots) and TCs (MSW of 34 knots or more) develop over the NIO during a year including 9 and 2 over the Bay of Bengal (BOB) and Arabian Sea (AS), respectively based on data of 1961–2010 (Mohapatra et al., Construction and quality of best tracks parameters for study of climate change impact on Tropical Cyclones over the North Indian Ocean during satellite era. In: Mohanty UC, Mohapatra M, Singh OP, Bandyopadhyay BK, Rathore LS (eds) Monitoring and prediction of tropical cyclones over the Indian Ocean and climate change. Springers and Capital publishers, New Delhi, pp 3–17, 2014). Out of these, about five intensify into TCs including about four over BOB and one over the AS. About three severe TCs (MSW of 48 knots or more) are formed over the NIO during a year. It includes two over the BOB and one over the AS. Considering the frequency of very severe TCs (MSW of 64 knots or more), there have been about two very severe TCs per year over the NIO. The frequency is maximum during post-monsoon season (October–December) followed by pre-monsoon (March–May) and monsoon (June–September) season.