A series of erroneous weather forecasts in the past few years has compelled the Indian Meteorological Department to formulate a new long range forecast model, which experts say would help predict the nature's vagaries more accurately.

This year's southwest monsoon rainfall season, which the meteorologists says would begin on June 1 at the Kerala coast, has been predicted by using the new 'eight parameter power regression model'.

Last year, they burned their fingers when a cyclone avoided their predicted path along the Chennai-Andhra Pradesh-Orissa coastline and ended up wreaking havoc in Bangladesh.

The meteorologists also predicted adequate rainfall last year, but severe drought hit across Northern India, considerably upseting the country's water supply and agricultural production.

According to IMD officials, the new model requires weather data only till March, unlike the old method in which the meteorologists depended on data till May for monsoon forecasts.

Basing its forecasts on the new method, the IMD has now come out with the probability of the monsoon rainfall for the country as a whole in 5 different categories: drought (less than 90% of long period average), below normal (90% to 97%), near normal (98% to 102%), above normal (103% to 110%) and excess (more than 110%).

A senior IDM official told rediff.com that the forecasts of the weather experts in the past were prone to errors as many of the parameters on which they based their assumptions declined rapidly over the years. "Our new method is physically well-related and statistically stable. We have now identified four new predictors of monsoon rainfall which are more reliable," the official explained.

He said that the IMD did not have any model, which could enable a modification to the long-range forecast once it was issued on May 25 every year. With the new model, which uses data up to June, it is now possible to generate a quantitative forecast update by mid-July. By that time, the nature of the advance of the monsoon would have become known, and any disturbing trends in the El Nino phenomenon would be apparent.

According to the new model of forecast, the 2003 southwest monsoon season (June-September) that begins on the Kerala coast is likely to be 96% of the long period average with a model error of ± 5%.

It is now to be seen whether the meteorologists' new method of weather forecast will be accurate that would lead to good rainfall and good agricultural production.

Meanwhile, next year, the ISRO will launch the INSAT 3B that would substantially boost meteorological capability and it is also planning a joint satellite project called 'MeghaTropiques', with French collaboration for an exclusive meteorology satellite that will be launched in 2006.