The India Meteorological Department (IMD) said on May 30 that the arrival of the southwest monsoon over Kerala has been delayed to June 3.
- IMD had last month forecast that the onset would be on May 31.
- Skymet, a private weather forecast agency, however, said the monsoon had arrived. This was because two of the three criteria — as defined by the IMD — had been met.
- The onset of monsoon over Kerala normally is June 1 which marks the beginning of the four-month rainfall season for India.
What are the parameters for onset of monsoon?
The onset of monsoon depends on these three parameters:
- If 60 per cent of available 14 weather stations situated in Kerala and coastal Karnataka namely Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Alappuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kudlu and Mangalore report rainfall of 2.5 millimetres or more for two days in a row the onset of monsoon of Kerala will be declared on the second day.
- Rain-bearing westerlies being at a minimum depth and speed;
- A certain degree of clouding, indicated by a parameter called ‘outgoing longwave radiation’ (OLR), being below 200 W/square metre.
