The Hindu Business Line : Monsoon revival likely by next week: Forecast

THE southwest monsoon may have lulled to a customary pause somewhere over the peninsula one month after onset, but it is expected to head off the intermission mode and rev into life in a week's time.

The unleashing of this `second spell' will mark the revival of the system over Central India, according to Dr M. Rajeevan, Director - Forecasting, India Meteorological Department (IMD), Pune.

"We expect the monsoon to revive by next week. In such a scenario, Kerala would possibly get another good spell," Dr Rajeevan told Business Line.

Explaining the significantly reduced rain activity over the peninsula, Dr Rajeevan agreed that there had indeed been a `lull' over the past few days. The official IMD forecast for 24 hours from Tuesday also mentioned about subdued rainfall activity over most parts of the country outside north-eastern States.

But this was only in keeping with the pattern of monsoon variability, says Dr Rajeevan. Subsequent to its arrival in Central India, the system was known to take a break. This might last for about a week. The revival would invariably come about with the second spell.

One active spell, the first of which saw the rain belt shift to Central India in the post-onset phase, might last for about 20-30 days followed by a lull. "We may have three to four distinct spells in this manner that last through the whole season," Dr Rajeevan said.

Lull period crucial: Significantly, the play-out of the period of lull would really decide the ultimate monsoon performance for the year.

"If the lull period extends to more than normal, we will have deficient rainfall. A very short lull on the other hand would presage a good monsoon."

The present lull did not classify itself as what meteorologists describe as the `break-monsoon' phenomenon. Break-monsoon is the interruption in monsoon rainfall by prolonged spells of sparse rainfall during the mid-monsoon months of July and August over the plains of northern India.

When a tropical low-pressure system moves from the plains in a northerly direction toward the submontane region of the Himalayas, the monsoon trough of low pressure also moves from the plains to that region. This deprives the plains of northern India of significant ascending motion and normal rainfall and brings about the break-monsoon.

The break-monsoon ceases and normal monsoon conditions are re-established when the monsoon trough returns to the plains and intensifies. This occurs in association with tropical low-pressure systems developing at or near the Bay of Bengal and moving toward the plains. The genesis and persistence of the break-monsoon, therefore, depends mainly on the interaction between the monsoon trough and tropical low-pressure systems of the Indian region.

IRI in agreement: Meanwhile, seasonal forecast issued for July by the International Research Institute for Climate Prediction (IRI) at Columbia University largely corroborated the IMD's long-range forecast of 100 per cent of the long period average issued on April 15.

According to Dr Rajeevan, the IRI forecast did not suggest any appreciable anomaly over the Indian region. The predictions suggested `climatological probabilities', or near normal rainfall.

In any case, the IMD proposed to come out with a monsoon update on June 29. "This time we will be issuing a forecast update for the country as a whole, a separate forecast for July rainfall and forecasts for four homogeneous regions of the country."

"Last year, we had covered only three — Northwest India, Northeast India and the Peninsula. This time, we would divide the Peninsula into two regions — Central India and South Peninsula — and have separate regional forecasts. Developing a forecast model for these small regions is a tough job. But we are at it," Dr Rajeevan said.

More Stories on : Climate & Weather | Kerala

Article E-Mail :: Comment :: Syndication :: Printer Friendly Page