The Hindu Business Line : Peninsular rains to rev up ahead of ‘low’

Thiruvananthapuram, Nov. 10 Rainfall activity over parts of the south peninsula, especially the extreme southeast, is forecast to scale up Wednesday onwards ahead of a brewing low-pressure area over southeast Bay of Bengal.

India Meteorological Department (IMD) has, on Monday, signalled the possibility of the ‘low’ intensifying into a depression, but stray international models ventured to predict a tropical cyclone in the basin.

The US Navy’s Fleet Numerical Meteorology and Oceanography Centre, the European Centre for Medium-Range Weather Forecasts and the Centre for Ocean-Land-Atmosphere Studies see a tropical storm (equivalent of a deep depression) swirling towards India’s southeast coast around Saturday (November 15).

The likely region of landfall could extend from the north Tamil Nadu coast (Chennai being a targeted area) to south coastal Andhra Pradesh, according to these models.

A trough of low persisted over southwest Bay of Bengal from Sunday with a cyclonic circulation over south Tamil Nadu and adjoining Sri Lanka. The other cyclonic circulation over Lakshadweep area and neighbourhood had become less marked on Monday.

Current meteorological analysis and numerical weather prediction models suggested that a western disturbance is likely to cause scattered to fairly widespread precipitation over western Himalayan region from Wednesday onwards.

The Climate Prediction Centre of the US National Weather Services has taken cognizance of several dynamical models suggesting the development of a La Nina during the unfolding northern hemisphere winter.

A La Nina in the making has implications for rainfall trends in India during the 2009 southwest monsoon. Observations by a few international models have been suggesting for sometime now that the equatorial Pacific was returning to a ‘base La Nina state’.

This contrasted with the ‘neutral’ (neither La Nina nor El Nino) status propounded by a group of others lead by the Australian Bureau of Meteorology. The US agency went on to add that La Nina becomes more likely if the current Madden-Julian Oscillation wave were to stall in a location that favours enhanced low-level easterlies and increased upwelling (and resultant cooling) in the east-central and eastern Pacific.

But it is rare for La Nina to develop late in the year, the agency said. Therefore, based on current atmospheric and oceanic conditions and recent trends, it said that ‘neutral’ conditions are expected to continue into early 2009.

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