The monsoon onset over Kerala, where the rains arrive first in India, is likely to be on June 5, with a model error of approximately four days, thereby delaying the onset of the southwest monsoon this year, the India Meteorological Department (IMD) said. The usual onset data as per IMD is June 1.
Last year, the forecast onset data was June 6 and the monsoon arrived in Kerala on June 8.
The IMD uses an indigenously developed state of the art statistical model for the forecast of monsoon’s onset data. Six predictors are used in the model –minimum temperatures over North-west India, pre-monsoon rainfall peak over southern peninsula, outgoing long wave radiation over south China sea, lower tropospheric zonal wind over southeast Indian Ocean, upper tropospheric zonal wind over the east equatorial Indian Ocean and outgoing long wave radiation over the south-west Pacific region.
The monsoon progresses to Kerala from Andaman and Nicobar Islands. This year, the IMD has revised onset dates due to the variability of rainfall and change in its patterns. As per the new normal dates of monsoon onset or progress, the southwest monsoon advances over the Andaman Sea around May 22.
The IMD said in a note that there is a low-pressure area over southeast Bay of Bengal and neighbourhood, which is likely to concentrate into a depression over the same region in the next 12 hours and it will intensify into a cyclonic storm by May 16 evening. The conditions associated with this event will help the advance of monsoon over Andaman Sea, Andaman & Nicobar Islands and southeast Bay of Bengal over the next 48 hours.
The advance of monsoon over Andaman Sea does not have a direct bearing on the onset of monsoon over Kerala.