DRP News Bulletin

DRP NB 170423:Forecast of Indian SW Monsoon & definition of normal monsoon

The India Meteorological Department (IMD) has on April 11, 2023 forecast that rainfall at national level in four months of June-Sept 2023 Southwest Monsoon will be 96% of Long Period Average (LPA). IMD considers Indian Monsoon rainfall as normal based on just one parameter of total rainfall in these four months at national level is between 96% and 104% of LPA, with model error of +/- 5%. This raises large number of questions as media has rightly raised post the IMD announcement.

Firstly, in a strange turn of events, on April 12, an update jointly by US weather agencies under the National Oceanic & Atmospheric Administration (NOAA), contradicted a number of assumptions of IMD the previous day, including the period when El Nino will become active and probability of it being a strong event, both of which have a strong bearing on the Indian Monsoon in an adverse way. So the first question that arises is, did the IMD not have the benefit of the observations on April 11 based on which NOAA made the forecast very next day? Or was it an attempt at providing an unjustified feel good monsoon forecast? This question arises as in the past too questions have been raised about such attempts by IMD. This question also becomes important as only a day or two before IMD’s forecast, private forecaster had predicted that monsoon rainfall is likely to be deficient and not normal.

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