The recent landfall of Cyclone Tauktae in Gujarat has caused immense destruction along the coastline states of Kerala, Karnataka, Goa, and Maharashtra. This tropical cyclone, which takes its name from the Burmese term for ‘gecko,’ was named by Myanmar. Typically, such cyclones develop during pre-monsoon and post-monsoon periods, with the most severe ones occurring in May-June and October-November.
Cyclone Classification
Cyclone Tauktae has weakened from an ‘extremely severe cyclonic storm’ to a ‘very severe cyclonic storm’. The India Meteorological Department (IMD) classifies cyclones based on their maximum sustained surface wind speed (MSW). They are categorized 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). For reference, one knot is equivalent to 1.8 kilometers per hour.
Arabian Sea’s Consecutive Cyclones
Cyclone Tauktae follows cyclones Mekanu (2018), Vayu (2019), and Nisarga (2020), making it the fourth consecutive cyclone to form in the Arabian Sea during the pre-monsoon period. Each of these cyclones since 2018 have been categorized as ‘Severe Cyclone’ or above.
The Rising Menace of Arabian Sea Cyclones
While the Bay of Bengal and the Arabian Sea combined produce an average of five cyclones annually, recent years have seen a shift in cyclone formation. Though the Bay of Bengal typically spawns four cyclones, warmer than average temperatures in the Arabian Sea resulted in three cyclonic storms in 2018. In 2019, five cyclones formed in the Arabian Sea, exceeding the Bay of Bengal’s three. Similarly, in 2020, while three cyclonic storms were observed in the Bay of Bengal, the Arabian Sea generated two.
Climatic Change: The Role of Global Warming
Meteorologists have linked this increased cyclonic activity in the Arabian Sea to global warming. The sea surface temperature has been on the rise for approximately 40 years, with an increase in the range of 1.2-1.4 degrees Celsius.
Tropical Cyclones: Formation and Intensification
Tropical cyclones are intense circular storms originating over warm tropical oceans. They are characterized by low atmospheric pressure, high winds, and heavy rain. The eye of the storm is a central region of clear skies, warm temperatures, and low atmospheric pressure. Tropical cyclones rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. Certain conditions contribute to the formation and intensification of these storms, which include a large sea surface with a temperature over 27° C, the presence of the Coriolis force, small vertical wind speed variations, a pre-existing low-pressure area, and upper divergence above sea level.
Naming of Tropical Cyclones
As per World Meteorological Organization guidelines, each region’s countries are to provide names for cyclones. The North Indian Ocean Region, covering cyclones formed over the Bay of Bengal and the Arabian Sea, encompasses 13 members, including Bangladesh, India, Maldives, Myanmar, Oman, Pakistan, Sri Lanka, Thailand, Iran, Qatar, Saudi Arabia, the UAE, and Yemen. The IMD, part of the Ministry of Earth Sciences, is one of the six Regional Specialised Meteorological Centres globally, designated to issue advisories and name tropical cyclones in the North Indian Ocean region.
