Though this is less than last year, which received 100 per cent of the long-term average rainfall against a forecast of 93 per cent, it is well within the normal range and should not be cause for concern.

“The error margin is five per cent which means it can be 100 per cent in the best case scenario,” said P S Goel, Secretary in the Ministry of Earth Sciences.

The forecast has been made as per a new model introduced this year with an inbuilt error of +/-5 per cent. This is the second time since 2002 that the IMD has had to discard its forecast model and opt for a new one. The 16-parameter Gowarikar model, in operation for over 14 years, was discarded in 2003 after the model failed to forecast the 2002 drought. The 8 and 10 parameter models, which replaced the Gowarikar model and were in operation for the last four years, have now been replaced by two forecast models — 5-parameter model for making an initial forecast in April and 6-parameter model for making the final forecast in June.

The weathermen declined to cate categorise the forecast — whether or not it can be called a normal monsoon — because the new model does not have any such category.

In the Gowarikar model, nationwide rainfall within the range of +/- 10 per cent of the long period average was termed as “normal rainfall”. In the models used in the last four years, nationwide rainfall within the range of 98 to 102 per cent of the average was termed “near normal”. The 4-month south-west monsoon season begins in June and the IMD will make a forecast in mid-May on the date of approach of the monsoon over the Kerala coast. “In the last week of June, we will make a forecast for the nationwide rainfall in July, a final forecast for the monsoon period and rainfall forecast over four homogeneous region,” said IMD director M Rajeevan.

According to Rajeevan, most parameters used in the forecast model were old, except one — the North Atlantic mean sea level pressure in May. The parameters have been selected to suit the changed scenario. The Ministry’s annual report, admitting the impact of climate change, said: “The findings indicate minor but perceptible shifts in the monsoon trough positions and strength of monsoon flow.”