Monsoon musings

The India Meteorological Department (IMD)’s first-stage forecast for the south-west monsoon for 2021 offers a spot of cheer amid the storm clouds gathering over the economy. It indicates that the quantum of rainfall this season is likely to be at 98 per cent of the long period average and estimates a 61 per cent probability of the country ending up with normal or excess rains. While a normal monsoon is obviously welcome as it could help agriculture GDP expand for the third consecutive year, policymakers, economy watchers and investors would do well to not get over-optimistic about the prospects for the farm economy, based on these preliminary forecasts.

IMD’s first-stage long-range forecast is generally too early to capture the evolving impact of phenomena such as the El Nino Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) that have proved to be critical swing factors influencing south-west monsoon performances in the past. Reading between the lines of IMD’s release this year, it is evident that it expects the current year’s monsoon to be less munificent than last year’s, when it expected rainfall at 100 per cent of the long period average with a 70 per cent probability of normal to excess rains. While neutral conditions now prevail on both the ENSO and IOD, IMD is watchful on negative IOD conditions developing as the season progresses. Last year, it was an unfolding La Nina that led to rainfall eventually exceeding IMD’s estimates at 109 per cent of the long-term average. Two, while IMD has been improving its record at foreseeing normal and excess monsoon years, it has tended to over-estimate rainfall in drought years such as 2002, 2009, 2014 and 2015. On this score, its second-stage forecast in June factoring in evolving weather conditions, is somewhat more reliable. There is also the fact that three consecutive normal monsoon years have been quite rare for India.

Given that the monsoon is no longer adhering to its historical patterns, there has been increasing demand from farmers and policymakers for more granular forecasts on its spatial and temporal spread. On this score, it is good to see IMD introduce a new dynamical Multi-Modal Ensemble forecasting system this year which will not just provide month-wise break-ups but also focus on rainfed agricultural regions. While the IMD is clearly making efforts to improve its forecasting abilities, the Centre and State governments are yet to properly use this valuable data, to appropriately guide cropping patterns, correctly estimate the demand-supply equation for essential crops, set trade policies and achieve a better state of disaster-preparedness against floods and famines that devastate individual districts every year.

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