Monsoon has made onset over Kerala and most parts of northeast India simultaneously on Thursday, May 30. It has made onset two days ahead of its normal onset date of June 1.
The normal date for monsoon onset over Kerala is June 1, thereafter it advances northwards, usually in surges, and covers the entire country around July 15. Monsoon normally advances over northeast India around June 5. But, during some years when the Bay of Bengal arm of the monsoon is active, monsoon advances over northeast India at the same time.
"The Bay of Bengal arm of monsoon is very active due to severe cyclone Remal which has pulled the monsoon flow over the region. There has been extremely heavy rainfall over northeastern states during the past two days. Moreover all monsoon onset criteria is being met over Kerala also during the past two days," said M Mohapatra, director general, IMD.
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If after May 10, at least 60% of 14 stations — Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kudulu and Mangalore — report rainfall of 2.5mm or more for two consecutive days, the onset of the monsoon over Kerala is declared on the second day, provided the wind pattern is south-westerly and Outgoing Longwave Radiation (OLR) is low. OLR represents the total radiation going to space emitted by the atmosphere or extent of cloudiness.
{{/usCountry}}If after May 10, at least 60% of 14 stations — Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kudulu and Mangalore — report rainfall of 2.5mm or more for two consecutive days, the onset of the monsoon over Kerala is declared on the second day, provided the wind pattern is south-westerly and Outgoing Longwave Radiation (OLR) is low. OLR represents the total radiation going to space emitted by the atmosphere or extent of cloudiness.
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Advance of the southwest monsoon over Indian main land is marked by monsoon onset over Kerala and is an important indicator characterizing the transition from hot and dry season to a rainy season. As the monsoon progresses northward, relief from scorching summer temperatures is experienced over the areas. According to India’s agriculture ministry, 51% of India’s farmed area, accounting for 40% of production, is rain-fed, making the monsoon critical. With 47% of the country’s population dependant on agriculture for their livelihood (according to this year’s Economic Survey), a bountiful monsoon has a direct correlation with a healthy rural economy.
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Monsoon rainfall over the country between June to September is likely to be "above normal" at 106% of long period average (LPA) with a model error of ± 5%, IMD said in its long range forecast on April 15.