Possible landfall between Karaikal and Mahabalipuram; southern states may get rainfall
Cyclone Nivar is brewing in the Bay of Bengal and might make landfall along the Tamil Nadu coast between Karaikal and Mahabalipuram on the afternoon of November 25, according to the India Meteorological Department (IMD).
However, any predictions by IMD have to be treated with caution as cyclones in the last few years have been highly unpredictable, mainly because of warmer waters in the Bay of Bengal, Arabian Sea and the Indian Ocean, a result of anthropogenic global warming.
Just this August, low pressure systems, which are the precursor storm systems to cyclones, during the monsoon season caused extremely heavy rainfall along a central belt across the country from Odisha to Gujarat.
According to Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology, Pune, one reason for the heavy rainfall in August was the unusually warm Arabian Sea.
Throughout August, the Arabian Sea was warmer than usual by two-three degrees Celsius. While the normal sea surface temperatures here are about 28-29°C, the temperatures this August reached up to 29-31°C.
The sea surface temperatures in the Bay of Bengal are also in the range of 29-30°C, according to IMD’s latest cyclone update.
A deep depression in October had also carried much more rainfall than normal, causing extremely heavy rainfall in many parts of Telangana and Andhra Pradesh.
Hyderabad witnessed one of its heaviest showers in the century and floods that brought large portions of the city to a standstill. More rainfall than normal is another concern around cyclones in a world of climate change.
Another important factor for cyclone formation and behaviour in this season would be the prevalence of the La Niña phenomenon in the equatorial Pacific Ocean.
On October 29 the WMO declared the prevalence of a moderate to strong La Niña event in the central and eastern equatorial Pacific Ocean. The phenomenon will continue till the end of the year and continue into the first quarter of 2021.
“La Niña tends to enhance cyclone formation and also higher category ones since during a La Niña they for further down in the tropics and travel longer,” Raghu Murtugudde, a climate scientist at the University of Maryland in the United States, said.
Murtugudde added that “this year has been a bumper year in the Atlantic so the Pacific and Indian Oceans are somewhat calmer. The total number of cyclones doesn’t increase that much so a higher number in the Atlantic tends to keep the numbers low in the other oceans.”
Nivar currently lies as a depression some 600 km south south east of Puducherry in the Bay of Bengal. It will intensify into a deep depression by the evening of November 23 and a cyclone by the morning of November 24. The wind speeds at the time of landfall are likely to be in the range of 100-110 kilometres per hour, with gusts of up to 120 km / hr making the storm a severe cyclone.
This will be first cyclone to make landfall on the Indian coast in 2020 and the second to form in the North Indian Ocean region after severe cyclone Gati in the Arabian Sea in 2020.
It might bring heavy rainfall to the southern states of Tamil Nadu, Andhra Pradesh, Karnataka and Telangana from November 24-26 but a close watch on its behaviour needs to be maintained.
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