IMD revises monsoon forecast down by 5% but let’s not say ‘drought’ yet

The Wire
June 4, 2015

From behind the thick curtains of the Indian Meteorological Department’s offices, it was announced on June 2 that the monsoon forecast for 2015 was being revised from 93% to 88% of the long-period average (LPA), ringing in fears of a drought.

The LPA hovers around 89 cm, computed using the rainfall received between 1951 and 2000. The forecast of 88% was made with an error of 4%, meaning the predicted amount of rainfall for the southwest monsoon, which lasts from June to September, ranges from 84% to 92% (74.76-81.88 cm). A normal or good monsoon is pegged at 96% to 104%.

The IMD’s annual forecasts form the basis of estimating crop yields in the country. Although the advent of groundwater irrigation that kicked in in the 1960s helped stave off losses due to deficient rainfall in the subsequent decades, reckless expansion unaccompanied by efforts to replenish the water means farmers will be back to writing off crops during periods of insufficient rains. It has already been suggested once that water supply will fall below 50% of demand by 2030.

At the same time, the basis of the IMD’s predictions are also suspect. The agency lists some 36 papers on its website that it uses as the basis of its modeling but does not provide the contents of those papers, making it difficult to verify its predictions. Alternatively, private forecasters like Skymet Weather disagree with the IMD’s outlook.

Skymet CEO Jatin Singh wrote on his site on June 2 that he’s sticking to his company’s prediction of a normal monsoon this year. The reason for his optimism? “… if the El Nino episode is a continuing El Nino from [the previous] year, the monsoon in the second year does not fail as often as it fails in the first year of evolution.”

The El Nino southern oscillation is a heating-and-cooling pattern of the waters of the Pacific Ocean along the South American coast. Its variations are influenced by trade winds along the equator, and in turn affects weather patterns worldwide.

Interestingly, an analysis performed by the Wall Street Journal earlier this year showed that, given even the generous 4% margin of error within which the IMD operates, it has got the annual monsoon levels right only six times in the last 21 years. Evidently, monsoon-forecasting in the country leaves much to be desired.