CHENNAI: The Regional Meteorological Centre (RMC) on Saturday issues orange and yellow alerts for Chennai and neighbouring districts predicting heavy to very heavy rain from October 14 due to upper air circulation prevails over the Bay of Bengal.
Chennai witnessed overnight showers for the last few days and as the northeast monsoon onset is likely to commence around next week.
Under the influence of a well marked low pressure area over the east central Arabian Sea with the associated cyclonic circulation it is likely to move west - northwestwards and intensity into a depression over the central Arabian sea by Sunday morning.
On the other hand, the upper air circulation over the central parts of the south Bay of Bengal lay over the southwest Bay of Bengal.
It is likely to trigger intense spells over coastal districts of Tamil Nadu from Monday.
On October 14, orange alert issued to Villupuram and Cuddalore districts and heavy rain warning given for Chennai, Thanjavur, Tiruvarur, Nagapattinam, Mayiladuthurai , Ariyalur, Tiruvallur, Chengalpattu, Kancheepuram, Tiruvannamalai and Kallakurichi districts.
The weather department has predicted heavy to very heavy rain over Chennai, Tiruvallur, Kancheepuram, and Chengalpattu districts.
Heavy rain is likely to occur over Cuddalore, Villupuram, Kallakurichi, Tiruvannamalai districts on Tuesday (October 15).
As per extended range predictions by dynamical models, near normal to above normal rainfall is likely over coastal and adjoining interior districts of Tamil Nadu. Also, below normal rainfall is likely over the plains of the rest of the state.
Normally, the northeast monsoon sets in around October 20, however, this year it is expected to be onset prior since the conditions are favourable over the sea. The RMC official stated that it is likely to commence around October 15. The northern parts of the state might witness above normal rainfall during the monsoon season.
According to RMC rainfall data, during October 1 to 12 Tamil Nadu recorded 77.6 mm of rainfall against the average 52.4 mm that is 48 percent excess rainfall.
Of which, the highest amount of rainfall reported in Tiruppur with 108.9 mm - 153 percent more spell, followed by Pudukottai 106 mm that is 150 percent of excess rainfall.