The Hindu Business Line : Fresh rain wave on, may skip interior peninsula

Thiruvananthapuram, July15 An offshore trough has sprung up over the Karnataka - Kerala coasts on Tuesday driving the first meaningful showers of the season over south Kerala.

The wet weather may hold over the next five-day period during when international models see a ‘low’ materialising over east-central and southeast Arabian Sea around June 18. This will boost weather prospects further in the extreme south peninsula.

The ridge (high pressure area) over southwest Arabian Sea is making the moisture-laden southwesterlies turn southeast along the Kerala coast and re-curve to blow north along Tamil Nadu coast.

TN COAST TROUGH

This in turn is forecast to throw up a matching trough along the Tamil Nadu coast, bringing rains into the interior southeast and along the coast. This trough would form under a cause-effect impact from a full-blown ‘low’ in the Arabian Sea.

The two formations on either side of the peninsula will together pack a wave of northward propagating rains. Forecasters are keenly watching if this ‘wave’ can propel itself fast enough to hasten some badly needed rain for interior peninsula.

But forecasts available on Tuesday did not make for an encouraging picture - the trough along the Tamil Nadu coast may collapse around July 20 and with it the rain wave. The Arabian Sea system would in turn decouple from the link across the peninsula and snap itself into position to the west of the Karnataka-Konkan coasts.

DRY INTERIOR

This would leave interior peninsula, especially west Maharashtra and north interior Karnataka, high and dry. These areas are forecast to receive rains only in September, according to July-1 forecasts made by the Tokyo-based Frontier Research Centre for Global Climate (FRCGC).

The FRCGC does not see much change occurring during the intervening August when excess rains are indicated for the southwest and southeast coasts; parts of central India, including Orissa, Chhattisgarh, Madhya Pradesh and south Gujarat.

But September rains are seen well over these ‘problem areas’, apart from Gujarat, Rajasthan and Tamil Nadu and Andhra Pradesh coasts. But less than adequate rains are indicated for interior Tamil Nadu, Orissa, West Bengal and the Northeast.

Writing to Business Line, Prof Toshio Yamagata, Director, Climate Variations Research Programme at the FRCGC, dismissed the notion that the positive Indian Ocean Dipole phase, which is seen driving the monsoon for a rare third consecutive year, was ‘over the peak.’

“We think the IOD is evolving still; we wonder how some people have reached the conclusion about its weakening. Our forecast suggests the IOD peaking over the next three to four months,” he added.

For sometime now, the IOD impact of positive rain anomalies has been reflected more to India’s northeast and near the Bay of Bengal, he added.

Prof Yamagata had led the FRCGC research team that discovered the IOD events of seesawing sea surface temperatures in the equatorial Indian Ocean. The IOD events have a greater and more immediate influence on the Indian monsoon than El Nino/La Nina.

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