Northeast monsoon
The Northeast monsoon between October and December accounts for 48% of Tamil Nadu and Puducherry’s annual rainfall.
PTI | File Image

The Northeast monsoon set in over Tamil Nadu, Puducherry, Karaikal and other parts of the south on Wednesday, even as the Southwest monsoon has withdrawn from the entire country, stated the India Meteorological Department (IMD).

Unlike other parts of India, Tamil Nadu and Puducherry are dependent on the Northeast monsoon between October and December accounting for 48% of its annual rainfall. In comparison, the southwest monsoon, accounts for only 35% of Tamil Nadu and Puducherry’s annual rainfall.

While the normal date of onset of the Northeast monsoon over coastal Tamil Nadu and south coastal Andhra Pradesh is October 20, this year the NE monsoon has commenced four days earlier, beginning October 16. 

In the year 2018, the onset of NE Monsoon over southeast peninsular India took place between 1 and 2 November, which meant a delay of 11 days from the normal onset date. This was due to extended Southwest monsoon activity. 

According to Wednesday’s 20.30 bulletin from Regional Meteorological Centre, Tiruvallur, Kancheepuram, Ariyalur, Cuddalore, Thiruvarur, Thanjavur, Nagapattinam, Ramanathapuram, Tirunelveli, Thoothukudi and Kanyakumari districts are likely to receive heavy rainfall in isolated areas on Thursday. Heavy rainfall is likely to continue in isolated areas of the state until October 20.

In Chennai, one or two spells of rain or thundershowers are likely to occur while the sky condition is likely to remain generally cloudy for the next 48 hours. Maximum and minimum temperatures in the capital city are likely to be around 31 and 25 degree Celsius respectively.

As of October 16, Poonamallee in Tiruvallur district recorded highest rainfall in the state, recording 11 cms of rainfall. Pamban in Ramanathapuram came second, recording 10 cms. Ayikudi in Tirunelveli and Cholavaram in Tiruvallur recorded 9 cms each. 

Weather blogger Pradeep John, who hands the Tamil Nadu Weatherman Facebook page, also wrote that rains with breaks will continue in Chennai. He also remarked on the importance of NE Monsoons for the districts of Ramanthapuram and Thoothukudi, both of which receive 80-90% of their annual rainfall during this period.

Rainfall recorded between 1 and 16 October, reveals districts like Coimbatore, Erode, Nilgiris, Ramanathapuram, Tirunelveli have recorded excess rainfall. Nilgris has recorded most rainfall during this period, measuring 190.4 mm as opposed to its normal reading of 104.6 mm. Ariyalur, Chennai, Cuddalore and Karaikal districts are among the top districts that have recorded huge deficits for this period in the state.