The India Meteorological Department (IMD) today said that the total rainfall in the country in the ensuing monsoon season (June to September) would be 95 per cent of the long period average rainfall with a prediction error of 5 per cent.

The actual rainfall in whole country during the season could be 90-100 per cent of the long- period average of 89 cm. This is considered normal rainfall and augurs well for agriculture as also for power production, navigation and other water-based economic activities.

This long-range prediction issued today will be updated in the last week of June taking into account additional relevant data available till then.

The IMD's will forecast the onset of the monsoon over Kerala in mid-May, officials of the IMD and the ministry of science and technology indicated today.

Last year, the IMD's long-range monsoon forecast released in April had projected the rainfall at 93 per cent of the average and the updated version issued in June-end had put it at 92 per cent of the average. However, the actual rainfall turned out to be 100 per cent though 9 meteorological sub-divisions remained rain-deficient.

This year, the IMD has again changed its statistical models for long-range monsoon prediction. The new models take into account five parameters each for making the prediction in April and its updated version in June. Three parameters are common in both the models.

The two earlier models used for rainfall projection in April and June were based on 8 and 10  parameters each. These models proved accurate in two of the four years in use.

Prior to 2003, a single statistical power regression model based on 16 parameters was used for monsoon prediction. That model was introduced in 1988, after the severe drought of 1987. It was scrapped after total failure in predicting 2002 drought.

Significantly, the IMD is using a new dynamic model for monsoon prediction as an experiment. The model, used for the first time, is deemed to be more accurate than statistical models for weather forecasting.

The dynamic model has also indicated the rainfall in the coming monsoon season to be near normal. "But this model needs more testing and validation before putting into actual use," IMD officials said.

The dreaded El Nino, which generally has adverse effects on monsoon, had developed in August 2006 but it dissipated fast to give way to La Nina that normally favours a normal monsoon.

The data collected by weather prediction centres abroad had indicated that La Nina conditions were likely to develop in the next three months, these officials said.