The Yaas cyclone recently hit south of Balasore in Odisha. A few days before this there was a cyclone named Tauktae. The Tauktae cyclone had affected Kerala, Gujarat, Maharashtra, Goa and Karnataka, including Daman and Diu and Lakshadweep.
- Yaas cyclone has been given this name by ‘Oman’. It is a word in Persian language which means ‘Jasmin’ in English.
- It is to be noted that tropical cyclones occur twice in the northern Indian Ocean region in the Bay of Bengal and in the Arabian Sea. The first cyclones develop pre-monsoon (between the period of April to June), while the second cyclones develop post-monsoon (between the period of October to December).
Classification of cyclones:
- The Indian Meteorological Department (IMD) has classified cyclones based on the Maximum Sustained Surface Wind Speed (MSW) generated by them.
- The cyclones are classified as severe (MSW of 48-63 knots), very severe (MSW of 64-89 knots), extremely severe (MSW of 90-119 knots) and super cyclonic storm (MSW of 120 knots or more).
- Cyclone Yaas is classified as a very severe cyclonic storm, as the speed of this cyclone was 90 to 119 nautical miles.
- The cyclone affected the border areas of West Bengal and Odisha and gradually the cyclone was weakened.
- In the region of Cyclone Yaas in the Bay of Bengal, in that region, in the month of May, the surface water temperature in the Bay of Bengal rises by at least two degrees above normal.
- This year, the northern part of the Bay of Bengal is normally warmer, with temperatures up to around 32 degrees Celsius.
- Tropical cyclones are intense circular storms originating in warm tropical oceans. Their main characteristics are low atmospheric pressure, strong winds and heavy rains. One of the distinguishing features of these types of cyclones is a cyclone’s eye or clear sky in the centre.
- Such storms are called ‘Hurricanes’ in the North Atlantic and eastern Pacific, and ‘Typhoons’ in Southeast Asia and China.
- Such cyclones in north-western Australia are called willy-willies. In the Southwest Pacific region and the Indian Ocean region, it is called a ‘Tropical Cyclone’.
- The movement of these cyclones is anti-clockwise in the northern hemisphere and clockwise in the southern hemisphere.
Favorable conditions for formation and intensification of tropical cyclones
- Large sea surface with temperature higher than 27° C.
- Presence of the Coriolis force.
- Small variations in the vertical wind speed.
- A pre-existing weak low- pressure area or low-level-cyclonic circulation.
- Upper divergence above the sea level system.
Nomenclature of tropical cyclones:
- The region or country in which this cyclone originates gives names to cyclones according to the guidelines of the ‘World Meteorological Organization’ (WMO).
- The tropical cyclone formed in the northern Indian Ocean region mainly covers the ‘Bay of Bengal’ and the ‘Arabian Sea’. The 13 member major countries in the region are Bangladesh, India, Maldives, Myanmar, Oman, Pakistan, Sri Lanka, Thailand, Iran, Qatar, Saudi Arabia, United Arab Emirates and Yemen.
- The ‘India Meteorological Department’ (IMD) is a major center among the six Regional Specialised Meteorological Centres (RSMC) in the world. It has the right to name tropical cyclones in the northern Indian Ocean region.
- The India Meteorological Department is an organization of the Ministry of Earth Sciences.
Cyclones of Bay of Bengal
- The water of the Bay of Bengal is concave or shallow. Here strong winds push the water forward with them, due to which it turns into a cyclone.
- The shape of the Bay of Bengal is like a trough. Because of this it is more susceptible to storms. Sea water is shallow, due to which the sea surface temperature is high, due to which the intensity of storms arising in the Gulf increases further.
- The absence of air movement from northwestern India towards the Gulf in the post-monsoon phase is also another reason for the possibility of a cyclone in the Bay of Bengal.
Arabian Sea cyclones
- The Arabian Sea region has very strong winds, due to which these strong winds dissipate the heat generated in this region. For this reason, this area is also very quiet.
- The flow of fresh water in the Arabian Sea is also less, because the water of rivers like the Bay of Bengal does not come here. This makes it easier for surface warm water and lower surface cold water to mix, resulting in lower surface temperatures.
- The Arabian Sea enjoys a local advantage as winds from the Pacific Ocean hit the Western Ghats and the Himalayas and their intensity decreases and sometimes never reaches the Arabian Sea.
Source: The Hindu