The current climatological outlook for southern India could change in the IRI forecasts from September if the tropical Pacific does warm further. It is possible that this could force a review of the forecasts, which for now "do not indicate any particular deviation from climatology for the southern Indian peninsula."

Vinson Kurian

Thiruvananthapuram, Sept. 1

US-based forecasters have indicated that the `normal' outlook for the impending northeast monsoon for south India could be subjected to a review depending on a warming trend in the Pacific Ocean.

NORMAL OUTLOOK

Earlier this month, the International Research Institute (IRI) for Climate and Society at the University of Columbia had retained the `normal' outlook for the season starting mid-October. Unlike in the case of the southwest monsoon, no official forecasts are available locally for the northeast monsoon.

Mr Tony Barnston, Director-Forecast Operations, Climate, Prediction and Dynamics at the IRI told

Business Line

that there is an increased likelihood of a weak El Nino (or a warming anomaly) developing in the east-central tropical Pacific in the coming month or two.

Warm ocean waters churn up strong moisture convection, which in turn fuels rain-driving weather systems.

SECOND LOOK

It is possible that this could force a review of the forecasts, which for now "do not indicate any particular deviation from climatology for the southern Indian peninsula," Mr Barnston said.

However, just in the last two weeks, there has been an increasingly significant wind situation in the west-central tropical Pacific - a westerly wind anomaly.

This, meteorologists suspect, could translate into an enhanced likelihood of a weak El Nino developing.

"Two weeks ago, when we developed our climate forecasts, we judged only about a 40 per cent chance of a weak El Nino. If the tropical Pacific does warm to a greater extent than we had expected, and we get anomalies of more than three-quarters of a degree C in the east-central tropical Pacific (now they are about one-half degree above normal), this may cause the Indian Ocean to warm by mid-October.

ENHANCED PROBABILITY

"When the Indian Ocean warms, there is a fairly good likelihood that the Bay of Bengal would also warm. This could then lead to an enhanced probability for above normal rainfall in the southern Indian peninsula - not necessarily (but possibly) through tropical cyclones, but just through a strengthening of the northeast monsoon winds and their moisture that would be released in the form of rainfall along the east coast of Tamil Nadu."

CLOSE WATCH

Given this, the current climatological outlook for southern India could change in the IRI forecasts from September if the tropical Pacific does warm further. While this may not definitely be going to be the case, it needs to be watched closely, Mr Barnston said.

In less than two weeks, the US National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Centre will put out a fresh discussion on El Nino-Southern Oscillation (ENSO). "We expect it to increase its assessment of the probability of a weak El Nino," he added.

(This article was published in the Business Line print edition dated September 2, 2006)
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