Storm seems to be moving towards the West Bengal and Bangladesh coasts after skirting the Odisha coast by October 25
Rapid intensification has often made cyclones much more powerful than they would have been otherwise. Photo: A screengrab from Windy. The cyclone in the Bay of Bengal, to be named Sitrang when it forms, may intensify into a severe cyclone October 25 2022, according to the latest national cyclone bulletin released by the India Meteorological Department (IMD) on October 22.
Its wind speed is likely to be in the range of 90-100 kilometres per hour, with gusts of 110 km per hour. The cyclone is also showing initial signs of rapid intensification in the forecasts, but it is too early to say anything for sure.
The weather agency has further predicted it would cross the Bangladesh coast between Tinkona and Sandwip islands in the Sunderbans. This is the first time that IMD has predicted a possible location for the landfall of the current cyclone.
This information should be taken with caution as cyclone formation, movement and intensification have remained quite unpredictable in the past few years.
At first, the current cyclone had created a scare for Odisha, where preparations had come into full swing. Even before that, many media outlets had created the scare of a super cyclone which was dispelled by IMD as mere rumours.
The storm seems to be moving towards the West Bengal and Bangladesh coasts after skirting the Odisha coast by October 25, according to the IMD.
In the evening of the same day, IMD also forecasts the cyclone to have wind speeds of 90-100 km/hr, which it qualifies as a severe cyclone. But the IMD has simply mentioned this wind speed category as a cyclonic storm in its bulletin, which could mislead authorities and people.
Any cyclone with wind speeds between 89 and 117 km/hr is a severe cyclone, according to the IMD.
The weather visualisation by the website Windy — using data from European Centre for Medium-Range Weather Forecasts — indicated a peak wind speed of 112 km/hr October 25.
All these could change drastically as the depressions had now formed and would move over the Bay’s warm waters in the next few days.
The low-pressure area (LPA) formed October 20 was situated in the north Andaman Sea and the southeast Bay of Bengal Thursday morning (October 21).
The weather department said the LPA then moved west and northwestwards and intensified into a depression (wind speed of 31-49 km/hr) Friday morning (October 22), kicking off the process of cyclogenesis.
It may further intensify into a deep depression (wind speed of 50-61 km/hr) Sunday morning (October 23) and subsequently into a cyclone (wind speed of 62-88 km/hr) by the evening of the same day, after changing its track north and northeastward.
Earlier, IMD’s expected date for the formation of the cyclone was October 24. This shows early signs of rapid intensification, which happens when a tropical cyclone gains wind speeds of 55km/hr or more in 24 hours. This happened in recent cyclones, such as cyclone Yaas and cyclone Tauktae in 2021.
Rapid intensification has often made cyclones much more powerful than they would have been otherwise. Warming ocean waters due to rising greenhouse gases in the atmosphere are to blame. The warm waters provide moisture for the cyclones to feed on and rapidly intensify.
Cyclone Yaas had kept IMD on its toes throughout its life cycle, showing rapid intensification and change in track before its landfall in north Odisha and moving into West Bengal.
Another factor that could impact its intensity and track even after landfall is the availability of excess moisture in the Sunderbans area and further up north over North East India. All these regions received excess rainfall in the first three weeks of October leading up to the cyclone.
East and northeast India received 34 per cent more rainfall than normal between October 1 and October 19, according to IMD.
The forecast of the track and intensification of the cyclone would now become more evident as the depression has formed. IMD would get further clarity once the system comes into the scope of a few of the eight doppler radars on India’s east coast.
Doppler radars are equipped with radio frequency technologies that can pierce through the cyclone’s outer winds to look at the cyclone’s inner winds, clouds and rainfall conditions. But their range is usually only a few hundred kilometres. The cyclonic system is currently more than 1,000 km away from the eastern coast of India.
This data is crucial in determining the behaviour of a cyclone, especially its path and intensification. Experts had told Down To Earth that the general conditions in the Bay of Bengal are conducive for cyclone formation and intensification.
The closest Doppler radar to the cyclonic system right now is the one in Visakhapatnam, while subsequently, the ones in Gopalpur and Paradip would have a better view of the cyclone.
Once the cyclone moves further northward, the radar in Kolkata would also be able to analyse the cyclone. This might help IMD with more accurate forecasts as the system comes closer to the coast for landfall.
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