North-East India and the southern peninsula have over the past few days remained the focus of the monsoon, which has weakened across the rest of the country.
An India Met Department said that entire Karnataka (comprising the north and south interior Met divisions) and the foothills of West Bengal and Sikkim saw ‘active’ monsoon conditions during the 24 hours ended this morning.
What continues to drive the rain over the southern peninsula is an upper air circulation sitting over south interior Karnataka.
It had drifted in from the southwest Bay of Bengal off the Tamil Nadu coast a couple of days ago and showed no signs of weakening this morning too.
It also enjoys the supporting environment set up by an east-west shear zone of monsoon winds high up in the atmosphere, where monsoon conditions are most active.
The presence of the shear zone boosts the monsoon performance over ground also.
Supporting environment
Another crucial meteorological feature helping the monsoon in these parts is a trough at the lower levels, extending from east Madhya Pradesh and cutting through south interior Karnataka linking Kerala.
Given these, the outlook for the next three days suggests heavy rainfall over the south and adjoining central peninsula, while being very heavy over the North-East.
Interior Tamil Nadu, Puducherry, Karnataka, Kerala, Lakshadweep and Madhya Maharashtra will share the spoils of the rainfall during the next three days.
The US National Centres for Environmental Prediction sees the circulation over south interior Karnataka strengthening by the weekend and erupting in heavy to very rainfall over the Kerala and Karnataka coasts on Saturday and Sunday.