12th time lucky, met predicts normal monsoon

The MET department’s forecast for the south-west monsoon’s rainfall between June and September this year is that the country would receive 99 per cent of its long period average (LPA), with an error factor of plus or minus 4 per cent. The LPA is the average rainfall calculated for 70 years from 1901 to 1970. The year’s rainfall is considered normal if it is within 10 per cent of 88 cms.

"The south-west monsoon has arrived over the South Andaman Sea on the expected date, May 15. It is progressing over the Bay of Bengal and North Andaman Sea," IMD Director General R R Kelkar told a Press briefing. "There has been good pre-monsoon rainfall activity over the north-eastern region which is likely to continue," he said.

Asked about the severe water shortage in north-western India, Kelkar said that even in the best of monsoons, there would always be some pockets where rains would be deficient. "Last year, Rajasthan, Gujarat, Saurashtra and Kutchh had a deficient monsoon. But this does not mean this year they will receive less rainfall. Some other pockets may have a deficient rainfall this year," Kelkar said.

Explaining the multi-parameter model that the IMD uses to make its forecast, Kelkar said that this year 10 out of 16 parameters were favourable, signalling another normal monsoon. This year the IMD has changed four of these to get a more accurate picture.

"The inclusion of four new parameters – the Darwin Pressure Tendency which registers pressure variations, sea surface temperatures of the South Indian Ocean and the Arabian Sea and the European pressure gradient – would remove statistical inconsistencies in the model," said Kelkar.

Other factors included among the 16 parameters are the El Nino Effect, Eurasian snow, East Coast minimum temperatures, central Indian temperatures, Indian Ocean equatorial pressures and the temperature and atmospheric pressure in the northern hemisphere.

The IMD’s forecast is that the rainfall this year is likely to be 102 per cent of the LPA over North-West India, which includes UP, Delhi, Punjab, Haryana, Himachal Pradesh, J&K and Rajasthan. In peninsular India, which comprises Gujarat, MP, Karnataka, Kerala, Tamil Nadu and Maharashtra, the LPA would be around 98 per cent. In the North-East region, including Arunachal Pradesh, Assam, Tripura, Nagaland, Manipur, Meghalaya, West Bengal, Orissa and Bihar, the LPA would be 100 per cent with an estimated model error of plus or minus 8 per cent.