The much awaited southwest monsoon set in over Kerala on Monday, thus keeping its usual date with the southern state, the India Meteorological Department (IMD) said.
Widespread rainfall was recorded over Kerala during the past two days. More than 70% of the 14 stations that monitor onset of monsoon in the state reported rainfall over the past 48 hours, the IMD said in a note announcing onset of the monsoon rains.
In its onset forecast, IMD had said monsoon will arrive in the country on June with a model error of ± 4 days
“Westerly winds have strengthened in the lower levels (wind speed upto 20 knots) and deepened up to 4.5 km over south Arabian Sea. “The Northern Limit of Monsoon passes is passing through Coonoor, Coimbatore and Kanyakumari,” the IMD said. The northern limit of monsoon is the line delineating the regions where the monsoon has advanced from the regions where the monsoon is yet to set in.
In the wake of cyclonic storm Amphan, there was a fear that monsoon onset might be delayed. However, the low-pressure area formed over Arabian Sea and conditions favourable for genesis of a cyclone have helped the onset of monsoon, IMD scientists said.
The IMD considers certain criterion for declaring onset of southwest monsoon over Kerala. Among them are rainfall recorded at 14 stations in Kerala - Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Alapuzha, Kottayam, Kochi, Vellanikkara (Thrissur), Kozhikode, Thalassery, Kannur, Kudulu (Kasargod) and Mangaluru after May 10.
If these stations report 2.5mm of rainfall or more for two consecutive days, the onset over Kerala is declared on the second day. IMD also checks for wind field depth of westerlies and outgoing long-wave radiation values.