“#JUSTIN Southwest #Monsoon2020 finally arrived on the mainland of India, #Monsoon arrived on Kerala before the actual onset date. All the onset conditions including rainfall, OLR value, wind speed, are met. Finally, the 4-month long festival begins for Indian. #HappyMonsoon (sic),” the private forecaster tweeted.
The onset of monsoon over Kerala marks the commencement of four-month rainy season in the country. The country receives 75 per cent of the rainfall from June to September.
Skymet had predicted that monsoon will hit Kerala on May 28 with an error margin of plus or minus 2 days. Whereas, the India Meteorological Department (IMD) had said the monsoon will make an onset over Kerala on June 5, four days after its normal onset date.
However, earlier this week, it said a cyclonic circulation in the Bay of Bengal will help in advancement of the monsoon and it could reach Kerala on June 1, its normal onset date.
IMD director general Mrutunjay Mohapatra said conditions are still not right to declare onset of monsoon over Kerala.
According to the IMD, there are three major conditions to declare the onset of monsoon.
The first is if, after May 10, 60 per cent of the 14 weather stations — Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Allapuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kudulu and Mangalore — report rainfall of 2.5 millimetres or more for two consecutive days, the onset over Kerala will be declared on the second day.
The second is the depth of westerlies should be maintained up to 600 hectopascals (hPa) and the third is the Outwave Longwave Radiation should be below 200 watt per square metre (wm-2).