Northeast monsoon to be normal, but more cyclones likely
CHENNAI: The Indian Meteorological Department on Friday said the southwest monsoon over India has officially ended with 6% excess rainfall and the onset of northeast monsoon, which contributes to 48% of Tamil Nadu’s annual rainfall, will begin around October 20 and is most likely to be normal.
Mrutyunjay Mohapatra, Director-General of the IMD, said, “Northeast monsoon rainfall over the south Peninsular India consisting of five meteorological subdivisions (Tamil Nadu, Pondicherry, Coastal Andhra Pradesh, Rayalaseema, Kerala and South Interior Karnataka) is most likely to be normal in the range of 88%-112% of Long Period Average (LPA).
The LPA of rainfall over south peninsular India during the October to December season based on data from 1971 to 2020 is about 334.13 mm. Besides rainfall, the northeast monsoon is notorious for tropical cyclones. On average, the season witnesses three cyclonic storms but this year there is a likelihood of more and also intense storms forming in Bay of Bengal due to prevailing La Nina and negative Indian Ocean Dipole (IOD) conditions.
Mohapatra told TNIE, IMD doesn’t provide a seasonal forecast for the cyclogenesis. “However, the past studies and based on preliminary analysis conducted by our team shows that during a La Nina year combined with negative IOD, which means warmer Bay of Bengal waters near Indonesia, the cyclogenesis activity goes up. This is based on past research findings and need not necessarily be true everytime. The latest Monsoon Mission Climate Forecast System (MMCFS) forest indicates that the negative IOD conditions are likely to weaken by the end of year. So, we have see how things change.”
Based on the weather models, the IMD sources said the chances of cyclones making landfall near north Andhra Pradesh, West Bengal, Odisha and even Bangladesh is higher than hitting Tamil Nadu.
The IMD said it was expecting the formation of a fresh cyclonic circulation in the Bay of Bengal during the weekend and any further southwest monsoon withdrawal was unlikely for at least a week.
Mohapatra said, “As the system formed in the Bay of Bengal will move westwards in the coming days, rainfall is likely to occur over Odisha, Jharkhand, UP and Madhya Pradesh from October 4 onwards. The presence of this system will stall the monsoon withdrawal from parts of central India. Unless it moves away and dissipates completely, there are no chances of monsoon withdrawal from central India at least till October 13.”
The normal date for the completion of monsoon withdrawal from the country is October 15.
As per the official statistics, during the southwest monsoon this year 1,322 people lost lives, of which 619 died in floods and heavy rains related incidents, while 696 died in thunderstorm and lightning strikes. In Tamil Nadu, four people had died.
Landfall not likely in TN
Based on the weather models, the chances of cyclones making landfall near north AP, West Bengal, Odisha and even Bangladesh is higher than hitting Tamil Nadu. The IMD said it was expecting the formation of a fresh cyclonic circulation in the Bay of Bengal during the weekend