Chennai: The rain spells continuing into 2025 in Tamil Nadu has brought forth the questiuon: Is this one of the longest northeast monsoon seasons? Since 2011, monsoons typically began after Oct 20 and extended to Jan but mostly ended before Jan 20. This one began on Oct 15, 2024, with withdrawal yet to be announced. IMD has forecast light rain in Chennai on Sunday followed by a dry spell, while five southern districts may get heavy rain, with more spells expected next week.
Blogger Pradeep John attributed the extended monsoon to the Madden-Julian Oscillation (MJO), a slow-moving tropical disturbance over Africa, the Indian Ocean, and parts of the Indian subcontinent.
One of the longest monsoons in the past was in 2004-05, when it began on Oct 18 and withdrew on Jan 25. In 2021, it arrived on Oct 25 and ended on Jan 22, 2022. The average onset is Oct 20 with a deviation of eight days, and withdrawal Dec 20 with a deviation of 14 days.
Experts say IMD considers parameters such as rainfall, depth of moisture, temperature, etc., for declaring withdrawal or cessation. IMD started announcing withdrawal dates of the northeast monsoon only from 1993. “Easterlies persist through Jan, with occasional spells until Jan 15-20. The spells may not be due to the typical weather systems of the Oct-Dec monsoon. Rainfall won’t completely stop during winters,” said N Senthamarai Kannan, Director, Regional Weather Forecasting Centre, IMD.
On Saturday, the city received light spells with rain gauges recording 0.5mm in some areas. On Sunday, mist/haze may form in the early morning followed by light spells. Temperatures may be at a maximum of 29°C-30°C and a minimum of 22°C-23°C. Light to moderate rain is also forecast at a few places over south TN on Jan 20 and 21. “Rain is due to a trough at 12,000 ft over Chennai extending to southwest Bay of Bengal. This is not typical monsoon rain,” said Mahesh Palawat, Chief Meteorologist, Skymet Weather.
