THE INDIA Meteorological Department Tuesday predicted a normal monsoon season this year, with total seasonal rainfall likely to be 96 per cent of the long period average, with model error of five per cent. Rainfall in the range of 96 per cent to 104 per cent of the long period average (LPA) is categorised as ‘normal’. The LPA, the average rainfall in the monsoon season over a 50-year period between 1951 and 2001, is 89 cm spread evenly throughout the country.
The coming monsoon season is likely to narrowly escape the expected adverse impacts of an El Nino event developing in the equatorial Pacific Ocean, off the western coast of South America. The El Nino, which refers to an unusual warming of the sea surface in the Pacific Ocean, is known to impact weather events worldwide and, in India, is associated with a suppressed rainfall during the monsoon season.
Although neutral conditions are prevailing in the Pacific as of now, global climate models are predicting a 50-per cent chance of the development of an El Nino in the second half of the monsoon season. However, a similar phenomenon in the Indian Ocean, called the Indian Ocean Dipole, is currently in a favourable condition.
“A weak El Nino is likely to develop in the Pacific Ocean while the Indian Ocean Dipole is currently positive. These two effects have opposing impacts on the Indian monsoon and are likely to cancel each other out. We are therefore hoping for a normal monsoon season this year and expecting a good regional and temporal distribution of rainfall as well,” said IMD director general K J Ramesh.
The forecasts for regional and month-wise distribution of rainfall during the monsoon season is made in May when the IMD comes out with a revised, second-stage, long-range forecast. Ramesh said that since the El Nino was still predicted to be weak, there was greater uncertainty in assessing its impact on the monsoon. While a more reliable estimate was likely to emerge closer to the start of the monsoon season in June, there was a distinct possibility of monsoon falling below the normal range — as of now.
The forecast of 96 per cent rains is at the lowermost border of the normal range (96 to 104 per cent) and the IMD said there was only a 38 per cent chance that it would reach ‘near normal’, or closer to 100 per cent, levels. Last year, the IMD had forecast that rainfall in the monsoon season would be 106 per cent of LPA. The actual rainfall, however, was only 97 per cent of LPA.