Tropical storm 'Damrey' has intensified into a typhoon (cyclone) over the South China Sea and is expected to hit the Vietnam coast by tomorrow.
Importantly, it is travelling in a remarkably straight path to the west, which would take a potent remnant into the Gulf of Thailand and further into the Andaman Sea/Bay of Bengal.
India Met Department (IMD) has already alluded to the formation of the low by November 7/8, which could further add to the Northeast monsoon currently lashing the Tamil Nadu coast.
The 'Damrey' remnant would have followed the track of a predecessor 'low' that moved into the Andaman Sea this afternoon, and is awaiting traction into the larger monsoon scheme of things.
It would achieve this by establishing a link with an existing and rain-spewing 'low' over South-West Bay of Bengal off Sri Lanka and Tamil Nadu coast.
The rain-generating capacity of a slow moving, even stagnant, 'low' such as this is of a much higher order than that of a cyclone during its fleeting run into and over land.
RAIN GENERATING CAPACITY
This is the threat which Chennai and the rest of Coastal Tamil Nadu have to contend with, as was proved in the widespread rain from overnight that has flooded many areas of the metropolis.
This offers a throwback to conditions witnessed in the devastating floods a couple of years ago, although the situation may have not deteriorated to those levels.
What is of concern here is the fact the existing 'low' would continue to prowl the waters of the Tamil Nadu coast and draw more strength from a 'low' that has moved in from the Gulf of Thailand.
The incoming 'low' had weakened into a trough in the Andaman Sea to the extreme south-east of Bay, but enjoys the twin advantages of a leisurely movement and extended travel over the waters.
SLOW SPEED, TRACTION
The bearing over waters extending into time and space in this manner allows it to grow by ingesting the moisture that associated winds mop up from the sea.
Model predictions also indicate that the current trough could intensify back into a 'low' and merge into the waiting counterpart off Sri Lanka and Tamil Nadu.
If this were to happen, this would make for a string of three 'low's and lead to even more rains for the coast. This is apparently what the weather tracker of the US Climate Prediction Centre points to.
Wind-field projections by India Met Department (IMD) tend to agree with the North-East monsoon flows expected to gain strength from Sunday.
Heavy rain has been forecast for the Tamil Nadu, Puducherry, and South Coastal Andhra Pradesh coasts during the next three to four days.