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Vinson Kurian

Thiruvananthapuram, July 13

A general slackening of the monsoon current in the second week of July has drained out two per cent from the 20 per cent surplus rainfall recorded during the ongoing season.

An update by the India Meteorological Department (IMD) said the surplus stood readjusted at 18 per cent as on July 11, as per available rainfall records. Still, 29 met subdivisions were able to hold on to excess or normal rainfall status (30, until the previous week).

The two per cent fall in surplus can be attributed to the diversion of monsoon flows into the west Pacific, capping the buzz in the peninsular seas. An outlook is still being maintained for a rather weak ‘low’ to form in the North Bay of Bengal but whose activity would be mostly best over Orissa, West Bengal and Jharkhand.

The western Indian Ocean still remains warm both at surface (as seen from sea-surface temperature graphs) and subsurface (as seen from heat content), according to Dr Swadhin Behera and Dr Toshio Yamagata of the Tokyo-based Frontier Research Centre for Global Change (FRCGC). This has helped bring heavy rainfall to Rajasthan, an otherwise dry region, they informed Business Line.

East Rajasthan has recorded a surplus rainfall of +77 per cent till now, followed closely by West Rajasthan (+68 per cent), as per the IMD update. “Perhaps, the active phase in the western parts of India will continue for a while even if we see a break-monsoon condition in the central and eastern parts,” the FRCGC researchers said.

The La Nina condition has not developed fast enough over the last month. But the eastern Pacific remains quite cold. “If this situation remains for a few more months, we might expect an ‘El Nino Modoki’ type of condition to develop in the tropical Pacific. During El Nino Modoki, the central Pacific remains warm flanked by cold anomalies on either side.” A typical case is that of 1994, a flood monsoon year for India.

In the Indian Ocean, the eastern cooling has not strengthened further. But the upwelling of favourable winds off Sumatra continues and strong easterlies persist in the equatorial eastern Indian Ocean. These will help to sustain the Indian Ocean Dipole (IOD) conditionwhich is monsoon-friendly. “Our coupled model prediction continues to predict a moderate IOD event,” the FRCGC researchers said.

Mr Jim Andrews of AccuWeather.com is of the view that the brewing weak ‘low’ in the Bay will move erratically towards the west and northwest lasting several days. It would seem that rain amount and coverage will increase somewhat from the east over the coming days. The US National Centres for Environmental Prediction (NCEP) says that rainfall will progressively cover the entire eastern quadrant of the country that houses the group of seven rain-deficit met subdivisions in the latest tally. A wet cover has also been predicted for the west coast during the week from July 13 to 20.

The NCEP forecast for the subsequent week (July 20 to 27) predicts a blow-up of rainfall to the extreme east and the northeast of the country matched by an appreciable shrinking of the wet cover along the west coast. Preliminary forecasts also favour a build-up of monsoon current to the south-southwest of the peninsula in what could possibly be the next incoming rain pulse that should end the lean phase.

The European Centre for Medium-Range Weather Forecasts (ECMWF) indicates some incipient activity around the Comorin/Sri Lanka region around July 23 but these are too early predictions for making any assessment.

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Weak monsoon trims surplus rainfall

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