Dry days: On rainfall deficit forecast

After the crest, the trough is inevitable. Following two years of surplus rainfall, India is likely staring at a significant shortfall in the coming monsoon. The India Meteorological Department (IMD) in its April forecast has predicted an 8% deficit, or “below normal” rainfall, coming June-September. There is a 5% margin of error in this estimate but going by IMD’s track record, there are many more times it has expected a ‘normal’ monsoon only for India to end up with a drought than it has forecast a drought and been proved wrong. In fact, when IMD warns of a deficit in April, history shows that India often experiences a drought. The agency, in its official lexicon, never uses the term ‘drought’ and only refers to a deficit below 90% as “deficient.” In the April of 2015, IMD issued a “below normal monsoon” forecast for the 2015 southwest monsoon season, predicting seasonal rainfall at 93% of the long-term average, again, ‘below normal.’ India ended up much worse at 86% Long Period Average (LPA). IMD expects a depressed monsoon this time in the second crucial half of the monsoon (August and September) on the back of weather models indicating an El Nino, the cyclical phenomenon where a heating of the central equatorial Pacific Ocean beyond 1 degree Celsius has corresponded nine out 16 times since 1950 to a deficient monsoon.

The timing of an El Nino matters. If the temperature rise happens outside of the monsoon months, its impact on the monsoon is not as threatening. In 2019, for instance, the IMD expected less than normal rainfall in April because El Nino-like conditions were on the horizon. Paradoxically, India ended up with above normal rainfall because that heating was not as strong as expected. This year too, the IMD expects the Indian Ocean Diapole would counter the desiccating impact of the El Nino. In a year where the most concerning clouds as of now are the war-like ones over West Asia, shortage of gas and fertilizer could worsen farmer sentiment on top of the weak rains. The government should immediately begin preparations to shore up fertilizer stocks, equitable water distribution, particularly in reservoirs that are likely to be stressed, and provide timely advisories to farmers on optimal sowing practices.