Despite the growing threat from a developing El Nino, the India Meteorological Department on Friday stuck to its earlier forecast of a normal rainfall during the monsoon season. The northwestern parts of the country, however, are expected to be a little drier, the IMD said. The country as a whole was likely to receive 96 per cent of its normal rainfall during the four-month monsoon season beginning in June. The northwestern parts, comprising of Punjab, Himachal Pradesh, Haryana, Jammu and Kashmir, western Uttar Pradesh, Delhi and some areas of Rajasthan are likely to get less than 92 per cent of their normal rains, IMD said in its updated forecast for the season. The three other major meteorological regions of the country – northeast India, central India and south peninsular India – are likely to receive normal or above normal rainfalls, between 94 and 106 per cent of their long period averages (LPA). Based on data from 1971 to 2020, the LPA, or ‘normal’, for northwest India is 587.6 mm of rainfall in the monsoon season, while it is 978 mm for central India, 716.2 mm for south peninsular India, and 1367.3 mm for northeast India. For the country as a whole, LPA during monsoon is 870 mm. The first month of the season, June, was likely to be slightly deficient. IMD said June was expected to produce only 92 per cent of the normal rainfall. The IMD said there was more than 90 per cent chance of an El Nino developing during the monsoon season. El Nino, or the abnormal warming of surface waters in the equatorial Pacific Ocean, impacts weather events globally. Over India, it has the effect of suppressing monsoon rainfall. IMD scientist D S Pai said there was a chance that the effects of El Nino could be offset to some extent by the development of a positive Indian Ocean Dipole (IOD). IOD is a similar phenomenon in the Indian Ocean. A positive IOD, when the western Indian Ocean becomes slightly warmer than the eastern side, helps monsoon rains. However, the impacts of IOD on the monsoon are not as strong as that of El Nino. Pai said that was one reason why northwestern India was likely to receive below normal rainfall. The impact of positive IOD is limited mostly to the southern peninsula and central India. Northwestern India was unlikely to benefit from the positive IOD. Of the 15 El Nino years between 1951 to 2022, nine saw less than 90% rainfall, while four resulted in 90 to 100% rainfall, and two years recorded more than 100%, according to data with the IMD. Pai said, like every year, there is likely to be variations in rainfall both in spatial as well as temporal terms. June, which normally brings 165.4 mm rainfall over the country as a whole, was likely to be deficient, expected to result in less than 92 per cent rainfall. The forecasts for the other three months would be issued later. The onset of monsoon over the Kerala coast was likely to happen around June 4, as predicted a few days ago. IMD said monsoon had advanced into some parts of southeast Bay of Bengal, Nicobar Islands and South Andaman Sea on May 19, and conditions were favourable for further advance over the Andaman and Nicobar Islands during the next two days. It said the progress of monsoon was expected to gain in strength around May 29.
