The existing low-pressure area over the South-East and adjoining East-Central Bay of Bengal (half way towards the Sri Lanka coast) stuck to its slow pace of evolution and lateral movement over the waters.
It is now expected to enter the South-West Bay of Bengal (nearer to Sri Lanka and South Coastal Tamil Nadu) over the next two days and become 'more marked.'
'PULL' FROM SOUTH
What prevents the 'low' from acquiring momentum is the battering its southern flanks have received from a system in the East Indian Ocean (to the South), moving exactly in the opposite direction (towards Sumatra).
Being South to the Equator, this depression-in-the-making moves to the east (unlike to the west above the Equator) and happens to be in close proximity to the path of the Bay of Bengal 'low.'
The latter may intensify in the South-East Arabian Sea only after the former spins away out of range, across the larger Indonesian archipelago.
Interestingly, this away-going system would, at the other end of the loop, partly trigger the formation of a potent 'low' in the South Andaman Sea by November 30.
According to the India Met Department (IMD) outlook, this 'low' would need close monitoring for signs of intensifying into a major weather system in the Bay in the first week of December.
HEAVY RAIN ALERT
In the short-term outlook, the IMD has predicted heavy rain would start lashing South Tamil Nadu as the current 'low' approaches its coast as well as adjoining Sri Lanka.
Satellite pictures this morning showed a ravenous-looking cloud bank, pausing just to the East of Sri Lanka, with a size that threatens to swallow the entire island nation.
The rains would last for at least three days, during when it would keep travelling to the west, crossing Sri Lanka and the tip of peninsular India to enter the Lakshadweep Sea, where it may intensify.
By this time, the Andaman Sea and adjoining South-East Bay of Bengal would have woken up to the new 'low,' and likely its rapid intensification, according to IMD forecasts.
The weather tracker of the US Climate Prediction Centre too has pointed to sustained activity in the Bay and the Arabian Sea during the last week of this month and the first of December.
It has maintained a heavy rain alert for parts of the Tamil Nadu coast into mid-December, which the IMD has referred to in its extended range forecasts.