The Hindu Business Line : Monsoon roars back to life, W. coast pounded

Thiruvananthapuram, July 1 The west coast, especially the Konkan-Mumbai-South Gujarat belt, has come in for a battering for the second time this monsoon in a pattern best attributed to a recurrent sea-based phenomenon – a positive Indian Ocean Dipole (IOD).

The west coast and parts of central India are witnessing what looks like a third successive surplus monsoon phase instigated by a rare third-in-a-row positive IOD event. India Meteorological Department (IMD) has now put the IOD on the same keel as the Pacific-generated El Nino/La Nina with regard to comparable influence on the monsoon.

Business Line had, on June 10, reported that the IOD event might just help the monsoon deliver more rain than what long-range forecasts appeared to credit it with. On Monday, the IMD upgraded its ‘near-normal’ long-term forecast (99 per cent of long period average) forecasts to ‘normal’ (100 per cent).

AIDING CONVECTION

A positive IOD occurs when the seesawing sea surface temperatures leaves a warming anomaly in the West Indian Ocean aiding convection and precipitation, with the pattern being reversed during negative IOD. In this manner, the monsoon gets an induced southwesterly ‘push’ that is reflected in the overall output over the landmass.

It is extremely unusual that a third consecutive positive IOD has evolved this year following those in 2006 and 2007. “As far as we know, there is no such occasion in the past 100 years when we had three consecutive positive IODs ”, Prof Toshio Yamagata and Dr Swadhin Behera of the Tokyo-based Frontier Research Centre for Global Climate (FRCGC), discoverers of the phenomenon, had told this paper.

On Tuesday, Prof Yamagata said it was a matter of time before operational weather agencies endorsed IOD as a crucial event driving weather in the region. The World Meteorological Organisation (WMO) and the Unesco have already embraced the concept. “I hope regional people have enough time to prepare for possible impacts the event may have on local weather.”

IMD on Tuesday said the rains would start spreading itself thin from July 4, but did not apparently press Monday’s outlook for the monsoon trough to retreat to the Himalayan foothills. This would normally have heralded the ‘break monsoon’, a normal cool-off period when the monsoon is noticeably active along the foothills.

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