The Hindu Business Line : Pacific cooling slows; monsoon outlook in tact

Thiruvananthapuram March 28 The Australian Bureau of Meteorology (BoM) has assessed that the cooling of the east and equatorial Pacific has somewhat slowed, but there is no case for drastically altering the outlook for a La Nina event.

La Nina is the colder counterpart of an El Nino where sea-surface temperatures ease in the equatorial and east Pacific and the warming anomaly shifts to the western Pacific, which is seen aiding the cause of the prevailing Indian monsoon.

Sea-surface temperatures in the central to eastern Pacific have remained close to average in March, following the rapid cooling that took place during January and February at the end of the 2006-07 El Nino event, the BoM said.

But there appears to be little chance of a return to El Nino conditions in 2007, with a continuation of "neutral" (to cool or warm episodes) or a switch to La Nina conditions, the more likely outcomes.

"El Nino conditions not likely to return" itself provides good reason to argue a case for a favourable monsoon, said Dr K.J. Ramesh of the Department of Science and Technology.

It does not really matter whether it is "neutral" or a full-fledged La Nina.

MONSOON OUTLOOK

Earlier, two respected models — the International Research Institute (IRI) for Climate and Society at Columbia University and the European Centre for Medium-Term Weather Forecasts (ECMWF) — have affirmed their outlook for a likely surplus monsoon for India this year.

The ECMWF has depicted a scenario wherein the Arabian Sea and Bay of Bengal arms of the monsoon build muscle respectively from the strong cross-equatorial flows across the Somali coast in the southwest Indian Ocean and deep convection in the South China Sea/West Pacific.

The IRI has estimated that there is "slightly enhanced probability" (up to 38 per cent) for an above normal monsoon this year.

The chances of a full-fledged La Nina event revealing itself are put at 50 per cent.

Meanwhile, an incoming westerly trough is threatening to assume strength of moderate intensity before hitting northwest India within the next two days, Dr Ramesh said.

Rain and snow in the hills apart, the system could generate high winds and hail in the plains of Punjab and Haryana. The unsettled weather will later travel to the east.

Contrary to expectations, the `ridge' (high-pressure area) building over North Pakistan/West Rajasthan has not grown in strength to repel an incoming westerly system. The ridge ultimately prepares the ground for a large anti-cyclone, which heats up the plains and sets up the `heat low' for monsoon current to drive in.

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