For the country as a whole, the seasonal rainfall from June 1 to September 30 was 105% of its long period average (LPA). LPA is the average monsoon rainfall from 1941 to 1990.

It arrived five days too early over the Kerala coast and left 15 days later from Rajasthan. By the time it made its delayed exit, South Peninsula was excess by 26% whereas North West was deficient by 15%, showing its uneven distribution.

Five subdivisions (West Uttar Pradesh, Haryana, Chandigarh and Delhi, Punjab, Himachal Pradesh and east Madhya Pradesh) experienced moderate drought conditions (rainfall deficiency of 26% to 50%) at the end of the season.

In both Central India and North-East India, it was marginally above the LPA.

In its end of the season report, the India Meteorological Department (IMD) admits that it was only the North-West and the North-East forecast that they managed to get right. The IMD, in its preliminary forecast in April, said that nationwide, rainfall this monsoon will be 5% less than the average. This had come as a surprise to those watching predictions put out by major international agencies which had indicated a “high probability” of above average rain, specifically over the western coast of India.

These included National Centers for Environmental Prediction, US; International Research Institute for Climate and Society, US; Meteorological Office, UK; European Center for Medium Range Weather Forecasts, UK; and Experimental Climate Prediction Center, US.

The Met department, which adopted a new forecasting model this year, had predicted 95 per cent rains before the onset of monsoon and later revised it down to 93 per cent in end June.

IMD has changed its model thrice in less than five years, making comparisons difficult. Last year, the IMD had predicted 93 per cent rains but the country went on to receive 100 per cent. This year it shifted to a new model, which it claimed, was more accurate. This has questions on the kind of model that IMD should use. Officially, they say the models used by these international agencies are technically sophisticated but are not geared to capture activities in the Indian Ocean once monsoon sets in.

While the IMD model is a statistical one—using data of chosen parametres ranging from temperature and wind to pressure over land and sea and comparing it with historical data— international agencies use models based on current dynamics and physics of the atmosphere and oceans, their main component being sea surface temperatures. With advancement in computing abilities, dynamic models are being preferred.

This year, IMD director general R C Bhatia repeated the doubts on the dynamical model in the Indian context. “As far as we know, the statistical models are the best. Even this model which we used this year was thoroughly tested and published in a reputed peer-reviewed journal before being adopted,” Bhatia said.

Will IMD change its model once again? “Yes, it has not been entirely accurate and we will conduct a review of the model very soon,” he said.