Season’s end: On the India Meteorological Department forecasts, rainfall deficit

The India Meteorological Department (IMD) issues two forecasts — in April and May — before the monsoon. Both unambiguously pointed to a dry monsoon — confidence boosted by global unanimity that one of the strongest El Niño ever was in the offing — and the consequential question was, ‘How bad?’ It turns out that the IMD’s forecast of ‘below normal’ rain (90% to 95% of average) was conservative. This was surprising, given that its models pointed to ‘deficient’ rains (below 90%). On September 30, when India’s monsoon tally ended, the IMD announced 759 mm across the country, 87% of the normal 869 mm. El Niño years, when the Central Equatorial Pacific warms and suppresses monsoon rains, test a weather department’s mettle because predicting the extent of the shortfall is challenging.