October ends with excess rainfall over T.N. for second consecutive year; IMD indicates below normal rains in November

October ended with excess rainfall over Tamil Nadu for the second consecutive year amid an active northeast monsoon. After a few days of dry weather, rainfall activity is likely to pick up marginally in the State from November 5.

The State has logged an overall rainfall of 23.3 cm, which is 36% above its normal share (17.1 cm) for October. Most districts ended the month with normal to above normal rainfall, while a few, including Ranipet, Tirunelveli, and Vellore, recorded largely excess rainfall following spells of heavy downpour.

In October 2024 too, Tamil Nadu had received 21.4 cm of rainfall, which was 25% above average for the month. This October, Chennai district too recorded surplus rainfall for the second consecutive year.

Chennai’s Nungambakkam weather station registered the second highest October rainfall of the decade with 32.4 cm. Last year holds the record for the highest October rainfall in Nungambakkam during the decade.

B. Amudha, Head (Additional in-charge), RMC said the NE monsoon has performed well over the past five years, bringing either normal or excess rainfall to the State. “This October, the State received rainfall almost daily except for the last few days. Active monsoon phase contributed to the excess rainfall,” she said.

Noting that the first few days of November will bring only dry weather over T.N., she said models indicated an increase in rainfall from November 5, with more clarity expected in one or two days.

Meanwhile, the India Meteorological Department (IMD) has forecast November rainfall in the State to be likely below normal rainfall. In its monthly rainfall and temperature outlook, the department has predicted rainfall to be below normal over most districts. The State is likely to experience an above-normal temperature except for a few districts along the western ghats.

In a long-range forecast based on the South Indian Ocean Convergence Zone model, a team of former meteorologists of the IMD, including Onkari Prasad, indicated a probability of normal rainfall in November. Districts such as Kallakurichi, Erode, and Tiruvarur may experience surplus rainfall.

Y.E.A. Raj, former Deputy Director General of Meteorology, said southwest monsoon rainfall in the first fortnight of October and early onset of northeast monsoon helped the State clock excess rainfall. The weather system in Arabian sea that persisted for over 10 days also accentuated the monsoon rainfall in T.N.

While the State has already recorded nearly half of its NE monsoon quota in October, the season, known for its alternating wet and long, dry spells may even out the overall rainfall distribution, he added.