Long dry spells predicted based on numerical models

The northeast monsoon, which set in over the State a few days ago, has so far yielded 19 cm rainfall, a little more than 50 per cent higher than the normal.

During the entire span of the monsoon, the State, on an average, gets 44 cm rainfall. Since 2004, the average rainfall was 56 cm.

On features of the monsoon, Y.E.A. Raj, Deputy Director General of Meteorology, points out that with the rainfall received, one should not immediately arrive at any conclusion about the overall behaviour of the monsoon. Long dry spells are indeed part of the monsoon.

“In a day or two, the rainfall will decrease and from Friday or Saturday, there may be a dry spell,” he says.

Adverting to numerical models, he says that a trough of low is lying over South Andaman Sea. As it acquires strength, it is likely to move northwards, probably skipping the coast of Tamil Nadu. In that event, the expected dry spell may become prolonged.

However, Dr. Raj hastens to add that the forecast is based on inputs available now.

A perusal of the district-wise rainfall data [hosted on the website of the Regional Meteorological Centre, Chennai] reveals that except seven districts, the remaining districts, as on Monday, registered surplus rainfall, going by the rainfall realised during October 1 to 22.

The seven districts — Ariyalur, Dharmapuri, Kanyakumari, Madurai, Namakkal, Perambalur and Salem — fall within the category of normal ones as their deviation from the normal is in the range of minus 19 per cent to plus 19 per cent. Of these districts, only Ariyalur has a negative departure value which is minus 1 per cent.

Heavy rainfall

In respect of Tirunelveli, Coimbatore and The Nilgiris, the figures of deviation have exceeded 100 per cent. Tirunelveli has registered 137 per cent with the actual rainfall of 23 cm; Coimbatore — 113 per cent (21 cm) and The Nilgiris — 101 per cent with 30 cm.

Chennai has received 25 cm rainfall with 49 per cent deviation; Tiruchi — 17 cm (29 per cent) and Madurai — 17 cm (10 per cent).

The districts that have recorded 20 cm rainfall and more are: Cuddalore — 27 cm; Dindigul — 25 cm; Villupuram — 24 cm; Nagapattinam, Sivaganga and Tiruvarur — 22 cm each; Ramanathapuram, Tiruvannamalai and Virudhunagar — 21 cm each and Tiruvallur — 20 cm.

An official said the toll due to monsoon is 24 so far.

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