Cyclonic circulation and strong easterlies trigger fresh rain spell over the State

Fresh spell of rainfall over coastal Tamil Nadu triggered by cyclonic circulation, expected to last till weekend.

A cyclonic circulation over Bay of Bengal and strengthening of easterlies triggered a fresh spell of rainfall over coastal Tamil Nadu on Wednesday. Isolated heavy rainfall that will cover coastal parts, including Chennai, on Thursday will drift to south and delta districts from Friday.

The rain spell, which is expected to last till the weekend, comes after fairly long subdued weather in the north coastal region except for a day of intense rain in some parts of Chennai on October 30. On Wednesday, various weather stations in the coastal region, including Chennai, Puducherry, Cuddalore and Thoothukudi recorded light rainfall till 5.30 p.m.

The Regional Meteorological Centre (RMC), Chennai, has predicted that the slow-moving cyclonic circulation over central parts of south Bay of Bengal would bring rainfall of light to moderate intensity in a few places of coastal Tamil Nadu on Thursday. One or two places in 11 districts, including Chennai, Kancheepuram, Chengalpattu, Thanjavur and Nagapattinam, may experience heavy rainfall up to 12 cm on Thursday.

It would be the turn of south Tamil Nadu and delta districts to receive heavy rainfall on Friday as weather system is inclined to move southwards along the coast, said officials. While many places in south Tamil Nadu are bound to receive rainfall, the RMC has said 15 districts and delta districts, including Theni, Tiruvarur, Ramanathapuram, Thoothukudi and Pudukottai have chances of heavy rainfall in one or two places. A similar weather trend may continue till November 10.

S.Balachandran, Additional Director General of Meteorology, Chennai, said the weak weather system would sustain moderate rain spell over various parts of the State for three days. The Madden-Julian Oscillation (MJO), a significant climatic factor that also influences NE monsoon over the State, is predicted to enter phase two over Indian Ocean by November second week. With the MJO pulse expected to pick up, this may be one of the factors that would help enhance monsoon rainfall from November second week, he said.

When the MJO is in phases two to four, it favours the NE monsoon and increases rainfall over Tamil Nadu. It is now in a weak phase and expected to enter phase two by November 12, Mr. Balachandran said. Meteorologists also noted that the NE monsoon is punctuated with prolonged dry spells.

Y.E.A.Raj, former Deputy Director General of Meteorology, Chennai, said November is the wettest month of the year and may compensate for the dry weather. With other climatic factors - El Nino-Southern Oscillation (ENSO)- remaining in neutral condition and weak La Nina, there may not be any direct impact of rainfall over the State as of now.