25th Jun, 2019
Cyclone Vayu hit Gujarat and ravaged port town.
- Cyclone Vayu is the second deadliest cyclone to hit the state since 1998 that had ravaged port town. It is the strongest cyclone in past 20 years.
What is Cyclone?
- Cyclone forms over different areas and revolve around low-pressure eye. Warm air rises and when it rises, it cools. Cool air cannot hold much moisture and so water gets squeezed out and clouds begins to form.
- If warm air rises quickly it creates updraft. Similarly, if the water in the clouds is build enough then it may fall into the ground in the form of rain and is known as downdraft. When they work together, a storm cell is created. This process continues, the cloud grows and we get a large thunderstorm cloud. These thunderstorm clouds are ready to diversify into other storms like tropical cyclone Vayu and tornadoes.
- Six factors responsible for the formation of cyclone: (1) Sufficient warm temperature at sea surface (2) Atmospheric instability (3) Impact area of Coriolis force so that low pressure can be develop (4) High humidity in the lower to middle levels of the troposphere (5) A pre-existing low-level focus or disturbance (6) Low vertical wind shear.
Impact of Cyclone Vayu on India
- It may cause a significant delay in the arrival of monsoon in some parts of the country.
- Coastal areas in Karnataka, Kerala, Konkan, Goa and Lakshadweep are also expected to receive fairly widespread rainfall.
Naming of Cyclones
North Atlantic Ocean and the eastern North pacific
Western North Pacific around the Philippines, Japan and China
Western South Pacific and Indian Ocean
Tropical cyclones or only cyclones
Cyclone Prone area in India
- According to the meteorological department, there are 13 coastal states and Union Territories in India are Cyclone prone region.
- Four states like West Bengal, Andhra Pradesh, Odisha, Tamil Nadu-and one UT Puducherry on the east coast and Gujarat on the west coast are more vulnerable.
Cyclone Warning System in India
- The India Meteorological Department is the nodal agency, which is responsible for meteorological observations, weather forecasting and seismology.
- A cyclone in the Bay of Bengal is predicted by the Area Cyclone Warning Centres (ACWC) and in the Arabian Sea it is predicted by the Cyclone Warning Centre (CWC).
- Both ACWC and CWC sent their report to National Cyclone Warning Centre (NCWC).
Naming of Tropical Cyclones
- The World Meteorological Organisation (WMO) has devised a mechanism where countries submit a list of names from time to time. Names of cyclones are chosen from this pool. The practice of naming these tropical cyclones in the Bay and Arabian Sea began in September 2004.
- For tropical cyclones developing in the North Indian Ocean, countries like India, Sri Lanka, Bangladesh, Maldives, Myanmar, Oman, Pakistan and Thailand send their names to the Regional Tropical Cyclone Committee.
- At present, all eight countries have submitted eight names each for naming future cyclones. The name Vayu was chosen from this list containing 64 names and was suggested by India.
- As per the existing list, the next cyclone that forms over the Indian Ocean will be named Hikka (Maldives), followed by Kyarr (Myanmar), Maha (Oman), Bulbul (Pakistan), Pawan (Sri Lanka) and Amphan (Thailand). Once the list is exhausted, the committee would meet again and a fresh list will be prepared by the Regional Specialized Meteorological Centre (SMC).
Difference between Arabian Sea and Bay of Bengal Cyclones:
- Bay of Bengal gets higher rainfall, and because the sluggish winds around it keep temperatures relatively high. Warm air currents enhance this surface temperature and aid the formation of cyclones.
- Bay receives constant inflow of fresh water from the Ganga and Brahmaputra rivers. This means that its surface water keeps getting refreshed, making it impossible for the warm water to mix with the cooler water below, making it ideal for a depression. On the other hand, the Arabian Sea receives stronger winds that help dissipate the heat, and the lack of constant fresh water supply helps the warm water mix with the cool water, reducing the temperature.
Exception to the rule
- Bay of Bengal witnesses cyclones both pre-monsoon and post-monsoon.
- The post-monsoon period sees a higher number of cyclones than the pre-monsoon period. This is because summers and pre-monsoons see dry and hot air moving from north-western India towards the Bay of Bengal.