The year 2020 has gone through a series of whirlwinds, not just the spread of novel coronavirus and its aftermath, but in the climatological sense as well.
India experienced five cyclonic storms--two in the Arabian Sea and three in the Bay of Bengal--in 2020, along with the formation of two depressions and two deep depressions. Of the five cyclones, one was severe, two--very severe and one super cyclonic storm.
A Cyclonic Storm or a Cyclone is defined as “an intense vortex or a whirl in the atmosphere with very strong winds circulating around it in anti-clockwise direction in the Northern Hemisphere and in clockwise direction in the Southern Hemisphere.” While the term "Cyclone" is derived from the Greek word "Cyclos" meaning the coils of a snake.
A disturbance having maximum average surface wind speed in the range of 34 to 47 knots (62 to 88 kmph) is classified as a cyclonic storm, while wind speed between 17 and 33 knots (31 and 61 kmph) is called depression/deep depression.
Whirlwinds in 2020
Amphan was the first Super Cyclonic Storm (SuCS) over the Bay of Bengal experienced in 21 years after the 1999 Odisha SuCS. The cyclone occurred in May (16-21) this year, affecting the two eastern states of West Bengal and Odisha. As many as 99 people lost their lives in West Bengal as per the official estimates, with no deaths reported in Odisha. More than 6 lakh houses were damaged, 23,965 cattle lost and 5.82 lakh hectare cropped area affected in these two states.
Nisarga was the first cyclonic storm that rose over the Arabian Sea in (June 1-4) 2020. This was also the first severe cyclonic storm (SCS) to cross Maharashtra’s coast in 59 years, the last one reported on May 24, 1961. While Phyan was the last cyclonic storm that crossed Maharashtra’s coast in 2009, prior to Nisarga. Fifteen lives were lost due to the SCS--Nisarga in Maharashtra, which also affected Gujarat and the union territories of Daman & Diu and Dadra & Nagar Haveli.
While Burevi was the last cyclonic storm recorded this year (November 30-December 5) over the Bay of Bengal.
On an average (measured between 1891 and 2017), five cyclones develop over the North Indian Ocean in a year, of which four are over Bay of Bengal and one over Arabian Sea.
However, the Arabian Sea alone reported five cyclones in 2019, against the normal of one per year, matching its previous record in the year 1902 for the highest annual cyclone frequency over the Arabian Sea, the government informed the Lok Sabha on September 23, 2020.
"In the recent past, increase in frequency had been observed in formation of cyclones in the North Indian Ocean. Also studies show an increase in frequency of severe cyclones over Arabian Sea in recent years," the government reply said.
