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An upper air cyclonic circulation has sprung up over the southwest Bay of Bengal off the Tamil Nadu coast signalling a take-off in the monsoon over south peninsula.
Upper air cyclonic circulations descend to lower levels to form low-pressure areas, and initial forecasts had suggested such a possibility not many days ago.
IGNITING MONSOON
But latest indications are that the circulation would cross the Tamil Nadu coast, move towards west-southwest to ignite a flare-up over coastal Karnataka and Kerala.
Along the way, another rain head would move west-northwest over peninsula and weave itself into a confluence of opposing winds over interior Maharashtra.
The ‘charge’ behind the escalating monsoon over the southwest is a passing Madden-Julian Oscillation (MJO) wave over the Indian Ocean.
MJO waves are responsible sudden surges in monsoon setting up onsets, low-pressure areas, depressions and even storms.
‘MISSING LOW’
These waves transit from east Africa into Indian Ocean but can touch off activity over ground, in this case southeast Arabian Sea, just off the southwest coast (Kerala).
US National Centres for Environmental Prediction is of the view that the ‘missing low’ in the Bay may show up over land in the melee being triggered over land.
The rains are forecast to continue to keep away from northwest India while getting heavy over northeast India and less so but widely spread over the peninsula.
This state of affairs may hold right until the end of the month, which is still 13 days away, and ahead of the beginning of withdrawal of the monsoon from the northwest.
RAINS IN EAST
Meanwhile, convective (rain-driving) clouds are moving east to east Uttar Pradesh, Bihar, and Gangetic West Bengal in the Himalayan foothills and adjoining plains.
They are also seen rising over Assam, Meghalaya, Sikkim, Nagaland, Jharkhand, Chhattisgarh and Odisha in clear signs that the heavy rain belt is shifting in here.
The seasonal trough in the northwest continued to hug the foothills Himalayas while the east extended into Bihar and onward towards Assam, Meghalaya and Nagaland.
To the southwest of the country, the offshore trough ran down from south Maharashtra to Kerala.
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