Days after US agencies predicted an early monsoon with above normal rains over parts of east and south India, the official weather forecasting agency, India Meteorological Department (IMD), has played it safe forecasting that monsoon rainfall over the entire country will be 93% of the normal index of 89 cm.

The normal index or the long period average (LPA) is the estimated average rainfall over the country in the four-month monsoon season beginning June, based on 100-year data.

As per the IMD’s old model—in operation until 2002—93% of LPA would have been called “normal” rainfall. The new model, however, has no such category as “normal” rainfall: between 98% to 102% of LPA is “near normal,” between 90% to 98% of LPA is “below normal” and below 90% of LPA is “deficient”

As the present model has a permissible error limit of +/-5%, there are chances of rainfall turning out to be 88% of the LPA, which according to new model would be termed “deficient.” There is also a possibility of rainfall turning out to be 98% of LPA, in which case it would be termed “near normal”.

However, the probabilistic model used by the IMD suggests that there is only 22% chances of “deficient rainfall.” Said IMD director-general B Lal: “Even though the forecast is for a below normal rainfall, there is no reason for panic. It may eventually turn out to be a near normal rainfall.”

IMD is scheduled to predict the onset date of the southwest monsoon at the Kerala coast in mid-May. In the first week of July, it will come out with a revised version of its forecast.

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