Monsoon onset 3 days ahead of schedule: IMD
NEW DELHI: The monsoon has set in over Kerala three days ahead of its normal onset date on June 1, India Meteorological Department (IMD) said on Sunday morning.
IMD forecast on May 14 said that the monsoon’s onset over Kerala was likely to be on May 27 with a model error of +/-4 days, five days ahead of its expected onset.
Most parameters to declare the monsoon onset remained unmet on Thursday, but there was a marginal improvement on Friday. “As per the latest meteorological indications, westerly winds have strengthened in the lower levels over the south Arabian Sea and deepened. As per satellite imagery, there is an increase in cloudiness over Kerala coast and adjoining southeast Arabian Sea. Hence, conditions are becoming favorable for monsoon onset over Kerala during the next 2-3 days. Further conditions are also favourable for the advance of Southwest Monsoon into some more parts of Arabian Sea and Lakshadweep area during the same period,” IMD said in a statement on Friday.
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 will be declared on the second day, provided the wind pattern is southwesterly and Outgoing Longwave Radiation (OLR) is low. OLR represents the total radiation going to space emitted by the atmosphere or the extent of cloudiness.
“The strength of the westerly winds have increased over southeast Arabian Sea in lower levels and is about 15-20kts(25-35kmph); cloudiness over southeast Arabian Sea and adjoining areas of Kerala have increased and the average outgoing long wave radiation (OLR) is 189.7 W/M2 (thus <200 W/M2) over the region; there has been widespread rainfall activity over Kerala during past 24-hours and out of 14 rainfall monitoring stations for declaring onset of monsoon over Kerala, 10 stations have received rainfall of 2.5mm or more. Thus, all the conditions for
onset of monsoon over Kerala have been satisfied today, May 29,” IMD said.
“Till Thursday only 33% of the stations in Kerala were getting rain. Today that has increased to 50%. The depth of westerlies has increased and cloudiness is there. We expect that soon the criteria for onset will be met. After the onset, we will issue a statement about its further progress and pace. We cannot immediately say whether it will progress immediately because the first onset should happen,” said RK Jenamani, senior scientist, national weather forecasting centre, IMD.
But on Sunday morning all these conditions were met, IMD scientists said. IMD will release details of the onset and further progress later in the day.