A prevailing cyclonic circulation (below the level of a low-pressure area) lying off Sri Lanka and South-East Tamil Nadu drenched the Tamil Nadu coast and parts of the interior on Monday as the North-East monsoon came into its own.
The India Met Department (IMD) has dropped enough hints to the effect that the circulation is here for the long haul and would benefit from the easterly flows beginning to grow in strength from the Andaman Sea.
The Thailand Met Department assessed that winds in the Gulf and the Andaman Sea have whipped up speeds of 35 km/hr with a wave height of one to two metres rising to above two metres offshore.
Winds in the rest of the Bay of Bengal are forecast to pick up speed as a low-pressure area forms in the Gulf of Thailand by Wednesday and crosses the southern Thai provinces to enter the North Andaman Sea.
The European Centre for Medium-Range Weather Forecasts assesses that the cyclonic circulation off Sri Lanka and Tamil Nadu would merge into a large trough linking it with Andaman Sea by Thursday itself.
This would in fact a set up a smooth ‘runway’ in the Bay of Bengal for the North-East monsoon flows and the weather systems (low-pressure area, depression) they might whip up in due course while approaching India’s South-East coast.
In fact, both the IMD and the European agency visualise not one but two such systems forming one after the other in the Gulf of Thailand and marching into the Andaman Sea by November 7.
The European centre is less optimistic here, and said none of the systems may grow to any significant strength within the Bay basin since no two systems can prosper at a given time.
All this while, the constant supply of moisture mopped up and carried onshore by the easterly winds would continue to precipitate as rain over the South Peninsula, especially along the Tamil Nadu and South Andhra Pradesh coasts.
The US Climate Prediction Centre sees the heaviest of the rain lashing Sri Lanka and extreme southern parts of peninsular India, i.e. South Kerala and South Tamil Nadu, during the week ending November 4 (Saturday).