- Cyclonic storm “Vayu” has intensified into a severe cyclonic storm, forcing authorities to put Gujarat on high alert.
- The State authorities have deployed teams of the National Disaster Response Force (NDRF).
- Cyclones developed in the regions between the Tropic of Cancer and Tropic of Capricorn, are called tropical cyclones.
- The weather conditions of low latitudes, mainly rainfall regimes, are largely controlled by tropical cyclones.
- Tropical cyclones usually develop in summer season in the vicinity of Inter-Tropical Convergence Zone (ITCZ)over warm ocean surface.
- Tropical cyclones are one of the mechanisms by which surface heat energy is redistributed from the equator to the poles.
Conditions necessary for development
- Tropical cyclones are formed due to low pressure of thermal origin. The conditions favourable for the formation and intensification of tropical cyclone storms are:
- Large sea surface with temperature higher than 27° C
- Presence of the Coriolis force
- Small differences in the vertical wind speed
- A pre-existing weak- low-pressure area or low-level-cyclonic circulation
- Upper divergence above the sea level system
Why West coast is less vulnerable to cyclones than East coast of India?
- Historical records suggest that for every four cyclones in the Bay of Bengal, there is only one in the Arabian Sea.
- Subtle differences between the way that convective currents behave over the Arabian Sea and over the Bay of Bengal may explain this higher frequency of cyclones forming over the Bay.
- Arabian Sea is cooler than Bay of Bengal.
- Fresh water from rivers fall into Bay of Bengal, making the water as a light thin layer, more prone to evaporation.
- There is a large-scale downward wind movement over the Arabian Sea during most of the year and convection has little chance to grow and intensify into cyclones.
- The areas along the coasts of West Bengal, Orissa and Andhra Pradesh are also flat which makes them especially vulnerable to landfall & inundation from storm surges and damage from the cyclone’s winds while due to significant height of Western Ghats landfall is a rare phenomena on western coast.
- Also, the Bay of Bengal is lying adjacent to the northwest Pacific, which is one of the world’s most active basins for typhoons. The region receives the remnants of major landfalls in the Philippines, China and South Asia.
Cyclones in India
- India has a very long coastline which is exposed to tropical cyclones arising in the Bay of Bengal and Arabian Sea.
- Indian Ocean is one of the six major cyclone-prone regions in the world. In India, cyclones occur usually in April-May, and also between October and December.
- The Eastern coastline is more prone to cyclones as about 80 percent of total cyclones generated in the region hit there
- The impact of the cyclones is mainly confined to the coastal districts, the maximum destruction being within 100 Km. from the centre of the cyclones and on either side of the storm track.
- The principal dangers from a cyclone include the gales and strong winds; torrential rain and high tidal waves (storm surges).
- Most casualties are caused by coastal inundation by tidal waves and storm surges.