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.

... contd.