The Hindu Business Line : `Above-normal' northeast monsoon forecast

THE International Research Institute for Climate Prediction (IRI) at the University of Columbia has predicted `above-normal' precipitation for southern India during October-November-December, a period coinciding with the northeast monsoon (post-southwest monsoon).

In its climate outlook for Asia during the season, the IRI said enhanced probabilities for above normal precipitation are predicted for southern India and Sri Lanka during the forecast period.

Northeast monsoon is the major period of rainfall activity over south peninsula, particularly in the eastern half comprising the meteorological subdivisions of Coastal Andhra Pradesh, Rayalaseema and Tamil Nadu-Pondicherry.

For Tamil Nadu, this is the main rainy season accounting for about 48 per cent of the annual rainfall. Coastal districts of the State get nearly 60 per cent of the annual rainfall and the interior districts get about 40-50 per cent of the annual rainfall.

Though the southwest monsoon is the principal rainy season for interior Karnataka, Kerala and Lakshadweep, rainfall continues till December in these sub-divisions, thanks largely to the northeast monsoon.

The increase in rainfall activity over Andhra-Tamil Nadu coasts around the middle of October is generally taken to mark the "setting in of northeast monsoon". Normal date of onset is around October 20 with a deviation of about a week on either side. India does not have a formal forecast system in place for the northeast monsoon.

Speaking to Business Line, Dr C.K. Rajan, Professor and Head, Department of Atmospheric Sciences, Cochin University of Science and Technology (Cusat), tended to agree with the prognosis from IRI. The unmistakeable imprint of global warming is evident in the climate pattern developing all over the world, of which the monsoon is a significant part.

Current trends indicate that the seas to the south of the central Bay of Bengal (as against the Head Bay) are warming up to the possibility of a few low-pressure systems, some of them intensifying into depressions, during the withdrawal phase of the southwest monsoon.

This is in keeping with the trend obtaining on a planetary scale in which an increasing number of destructive systems (hurricanes in the north Atlantic and typhoons in the Pacific) have spelt disaster after crossing land.

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