The anxious wait for the onset of the southwest monsoon is finally over as a weather bulletin issued by the India Meteorological Department on Friday afternoon declared that it had set in.
“Southwest monsoon has set in over Kerala on Friday against the normal date of June 1,” the weather bulletin said.
“It has further advanced into entire south Arabian Sea, some more parts of central Arabian Sea, entire Lakshadweep area and Kerala, some parts of coastal and south interior Karnataka and Tamil Nadu, remaining parts of southeast Bay of Bengal and some parts of central and northeast Bay of Bengal,” it said.
It further added that the conditions were favourable for further advance of southwest monsoon into some more parts of central Arabian Sea, Karnataka, remaining parts of Tamil Nadu, some parts of Rayalaseema and Coastal Andhra Pradesh, some more parts of central and north Bay of Bengal and southern parts of northeastern states during the next 48 hours.
The onset’s announcement was a mere formality, as on Friday morning many parts of Kerala received heavy rains, which started last night.
To declare that that the monsoons have arrived in Kerala the data recorded at the 14 weather stations located at Lakshadweep, Kerala and in Mangalore was being closely monitored.
The officials monitor the rains starting May 10. If 60 percent of the stations or more record 2.5 mm of rain for two continuous days, it satisfies the criterion that monsoon has arrived.
Another yardstick that the IMD uses is the strength of the wind. Cloud movements are also a key indicator for the weathermen when it comes to announcing the monsoon.
The IMD report shows that in the past one decade the operational forecasts were correct. But this time it failed as the forecast date was May 30, with a model error of plus or minus four days.
And now that the southwest monsoon has set in, it advances northwards, usually in surges, and covers the entire country around July 15.