The monsoon seems set to hit the south Andaman sea and south Bay of Bengal around May 19 and the Kerala coast around May 30, close to the normal date of June 1.
Meteorologists said rainfall activity over the bay islands was expected to increase as favourable conditions were building up for the air-mass of the south-west monsoon to hit the south Andaman sea and the south Bay of Bengal around May 18.
Normally, the monsoon hits south Andaman around May 15 and the south Bay of Bengal around May 20. A difference of five days on either side is deemed normal. Last year, the monsoon had arrived in this region on May 26, around 11 days behind schedule.
It is the Arabian sea current of the monsoon that generally arrives on the Kerala coast.
Normally, there is a gap of 10 days between the Bay of Bengal current's arrival in the Andaman region and the Arabian sea current's arrival on the Kerala mainland.
National Centre for Medium Range Weather Forecasting (NCMRWF) Director Akhilesh Gupta told Business Standard that normal onset in both the directions indicates a normal monsoon.
The centre's prediction model suggested the beginning of persistent rainfall activity in the Bay of Bengal region from May 18.
The monsoon is likely to break over the region on that day or a day later. The centre has not made any forecast about the Arabian-sea current.
The prediction of the monsoon hitting the Kerala coast on May 30 has come from the India Meteorological Department (IMD). "There could be a difference of three days on either side," said an IMD spokesman.
Gupta said the Bay of Bengal current was usually not very strong in the beginning and there might be a break in the rainfall before it advanced towards the mainland.
The Arabian Sea wing was usually characterised by a strong current which could normally sustain its forward surge to hit the Kerala coast and advance towards the interior.
He added that La Nina (cooling of sea water in the Pacific region), that normally ensured good monsoon rainfall in India, had slipped to neutral from the earlier slightly positive state.
La Nina is the opposite of the dreaded El Nino (warming of the Pacific ocean) that generally has a bad influence over monsoon rainfall in the region. It will have to watched for some more time.
Last year, though the monsoon had hit the Bay of Bengal and south Andaman sea on May 26, it entered the extreme south Arabian Sea in the first week of June.
The onset of the monsoon over Kerala was on June 5, four days behind schedule. After this, it resumed its forward journey on June 16.
In the north-east, the monsoon arrived on June 16, two weeks behind the normal date. Thereafter, it covered the entire country by June 30, almost two weeks ahead of schedule. There were only seven prior occasions when the monsoon covered the entire country in June itself.