The India Meteorological Department (IMD) has extended by one more day till Tuesday the expected timeline for intensification of the latest low-pressure area over south-east Bay of Bengal and adjoining east equatorial Indian Ocean, with a track aimed towards the Sri Lanka and Tamil Nadu coasts. The system had failed the originally set timeline on Sunday itself.

The ‘low’ is likely to move in a typical west-northwest direction and become ‘more marked’ (signalling a first round of mild intensification) in next 24 hours, the IMD said in an update on Monday afternoon. 

Can cut both ways

Delay in lateral movement of the system can either ensure time and space for intensification (as in case of predecessor cyclone Fengal) ortotal loss in forecaster’s confidence of survival of the system. At 2.30 pm on Monday, the US Joint Typhoon Warning Centre had also assessed as ‘low’ its chance for development to next level at least for another day. 

The IMD said the low-pressure area, or its slightly intended variant, is likely to continue to move west-northwest, and enter the seas off Sri-Lanka–Tamil Nadu coasts by Wednesday, without indicating where and when the landfall might take place. 

Heavy rain likely

Westerly winds from the opposite side will prevent a fuller blast of the incoming rain wave over the coast by shearing the top of the system and producing a drag on it. Still, it would be able to bring heavy rain at isolated places very likely over Tamil Nadu, Puducherry and Karaikal for four days from Tuesday. Isolated very heavy rain is likely over the region on Wednesday and Thursday. 

Elsewhere, heavy rain is predicted at isolated places over coastal Andhra Pradesh and Yanam and Rayalaseema, just to the north, for three days from Wednesday. Heavy rain is likely at isolated places over Kerala and Mahe to the west for three days from Thursday, and at isolated places over south interior Karnataka on Thursday and Friday. 

More rain waves seen

Light to moderate rain, thunderstorms and lightning are likely at a few places over Tamil Nadu, Puducherry and Karaikal and Kerala and Mahe for five days; and over coastal Andhra Pradesh and Yanam as well as Rayalaseema on Wednesday and Thursday. 

Meanwhile, numerical models of IMD as well as European Centre for Medium-Range Weather Forecasts have retained outlook for a follow-up easterly wave/low-pressure area impacting the Tamil Nadu coast from Monday next (December 16), and possibly a third, three days hence. Some other models indicate wet envelope over Tamil Nadu persisting until as late as December 25.