Monsoon forecast needs more detailing

IMD predicts ‘normal’ monsoon; the worry is over distribution

There are varying forecasts of this year’s South-West monsoon, with the India Meteorological Department (IMD) and the private weather agency Skymet offering different projections. IMD has predicted a normal monsoon with rainfall estimated at 96% of the long-period average (LPA); Skymet has projected a below-average seasonal rainfall at 94% of the LPA.

Both the forecasts have an error margin of plus or minus 5%. The Skymet forecast is near the higher end of 'below normal' and IMD forecast is near the lowest end of 'normal'. The difference between the two over a four-month period may not mean much, especially when it is known that weather forecasts can be unreliable. All weather events like the monsoon are influenced by a number of factors.

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IMD does not think that El Nino, the Pacific Ocean warming phenomenon, will have a major negative impact on the Indian monsoon this year because of other countervailing factors.

If the IMD forecast turns out to be correct, it will be the fifth straight year when the South-West monsoon will be normal or near normal. But experience has shown that it is not just the total quantity of rainfall over a period that is important.

India is a diverse country with varying geographies, crop patterns and agricultural practices. The monsoon is still the most influential factor in the country’s agriculture and it has a major influence on the economy, too. The spatial and temporal distribution of rainfall is much more important than its total quantity. Agricultural operations have different timings across the country, based on the traditional progress of the monsoon. If this schedule is disrupted, even normal rainfall, by quantum, will not help the farmer. The absence of rains at a time the farmer needs them and rainfall when it is not needed can only do damage.

IMD has not been able to make accurate predictions of such distribution. It makes a more detailed prediction before the onset of the monsoon, but that does not meet the need for forecast for a specific area over a specific period. IMD has yet to develop the tools and expertise for that.

The situation is compounded by the occurrence of extreme climate events, attributed to climate change. Excessive rainfall, failure of precipitation, heat waves, changing wind patterns and other extreme events have become much more frequent and have affected everything from sowing to harvesting and crop outputs. Last year, wheat production suffered a major decline because of a heat wave, though the rainfall was normal. So, the Union and state governments will have to be prepared for both normal and below-normal rainfall and for extreme weather events, and be able to formulate steps to face any eventual situation.