Private weather forecaster Skymet on Monday questioned the India Meteorological Department’s (IMD) announcement that the southwest monsoon arrived in Kerala on Sunday, three days ahead of the “normal” date.
“Declaring monsoon based on single day observations amounts to gross violation of standards, never attempted in the past,” Skymet said. Going by what it called “specified objective criteria” for forecasting monsoon arrival, the agency said, “Monsoon does not seem to be kicking up soon over Kerala and Peninsular India.”
An IMD official, however, told FE that the department had “complied with all parameters to predict the onset of monsoon. “We don’t want to react to statements made by any private agencies,” he said.
Earlier, Skymet had forecast monsoon reaching the Kerala coast on May 26 while IMD’s initial forecast was May 27. On Friday, the official weather agency said monsoon would arrive in the Indian subcontinent “in the nxt two to three days”. On Sunday, it confirmed the onset.
IMD and Skymet had such spats in the past too. For instance, in 2013, both differed on whether the showers over north India during mid-June that year were monsoon rain. IMD said it was indeed monsoon, Skymet asserted it was pre-monsoon freak shower.
Skymet said: “Onset of monsoon has specified objective criteria comprising of rainfall, winds and outgoing long wave radiations (OLR). If after May 10, 60% of the available 14stations, viz Minicoy, Amini Divi, Trivandrum, Punalur, Kollam, Alappuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kudulu, and Mangalore report rainfall of 2.5mm or more for 2 consecutive days, the onset over Kerala be declared on the 2nd day, provided the winds and OLR criteria also remains in concurrence.”
It added that “today (Monday), 7 out of the 14 earmarked stations have recorded nil rainfall and 2 more locations have registered less than 1mm. Most locations with fair amount of sunshine fail to give the monsoon feel … Most areas of Tamil Nadu, Karnataka, Kerala and Rayalaseema will have to wait to catch up with proper monsoon stream”.
While forecasting the onset of the annual weather phenomenon on Sunday, IMD had listed out the conditions that were satisfied for declaration of onset of monsoon over Kerala namely “the depth of westerly winds is extending up to 4.5km above sea level, the strength of the westerly winds have increased over southeast Arabian Sea in lower levels and is about 25-35kmph, increase in cloudiness over southeast Arabian Sea and adjoining areas of Kerala and the average OLR of 189.7 W/M2 (thus <200 W/M2) over the region.
It had also noted “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”.
Both IMD and Skymet have forecast a normal monsoon for the fourth year in a row. Last month, IMD had said India would receive a ‘normal’ monsoon (June-September) at 99% of the benchmark long period average (LPA), with a model error of +/- 5%. Skymet said monsoon would be ‘normal’ at 98% of LPA, with an error margin of +/- 5%.