Northeast monsoon likely to be normal over Tamil Nadu: IMD

The much-awaited Northeast monsoon, which accounts for a substantial share of Tamil Nadu’s annual rainfall, is likely to be normal this year, according to India Meteorological Department (IMD).

Northeast monsoon has assumed greater significance this year, coming on the heels of a deficit southwest monsoon rainfall.

The State usually receives an average of 44 cm during the NE monsoon. While south and coastal Tamil Nadu are likely to receive normal to above normal rainfall, north interior districts are predicted to receive below normal during the ensuing monsoon. Conditions are favourable for the onset of the monsoon from October third week, said IMD Director-General Mrutyunjay Mohapatra during a virtual press briefing on Wednesday.

Many parts of the State may experience normal to above normal rainfall in October except parts of north Tamil Nadu that may receive below average rainfall. The State may have to brace for above normal maximum and minimum temperatures in October too.

The State has recorded a below average rainfall this Southwest monsoon, with deficit of 20%. Many districts, including Nagapattinam, Karur, Thanjavur, Thoothukudi and Chengalpattu, have recorded deficit above 35%. (September 30 is considered the official end of SW monsoon by IMD).

During El Niño years, weather systems usually move towards Tamil Nadu, south Andhra Pradesh and Sri Lanka during NE monsoon and development of low pressure systems can determine increase in rainfall activity, he said.

The prevailing strong El Nino conditions may further strengthen till the year-end and neutral Indian Ocean Dipole may continue during NE monsoon as well. A positive IOD is usually considered favourable for good NE monsoon.

Meanwhile, the Regional Meteorological Centre has forecast a wet spell over the Western Ghats and interior parts of the State till the weekend. However, temperatures are likely to remain near normal from October 1.

A north-south trough extending up to Gulf of Mannar will influence wet weather over the State. Heavy rainfall may occur at one or two places over Nilgiris, Coimbatore and Erode districts on Thursday. Interior districts may experience moderate rainfall.

V.R. Durai, Head, Regional Weather Forecasting Centre, said various places are experiencing hot weather as dry westerlies prevailed over the region. While attributing simmering heat in interior parts partially to strong El Niño, one of the global weather parameters, he said the State is currently in the transition phase from Southwest monsoon to Northeast monsoon. A reversal in wind pattern and increased cloud cover would help bring down temperatures.

At present, temperatures are likely to fall only in places that receive rainfall. Mild rainfall may continue in some parts until October 6, he said. While Chennai may experience above normal temperature of 36-37 degrees Celsius on Thursday, the RMC has also predicted possibility of light rainfall in some areas.