Rainfall on the east coast of Tamil Nadu occurs during October to November due to

Answer: (b) Retreating south-west monsoon

October–November belongs to the retreating monsoon season. Moist north-easterlies and Bay of Bengal weather systems bring rain to the Tamil Nadu coast during this transition.

The idea

During autumn, the summer monsoon withdraws and the low-pressure belt shifts south. North-easterly winds crossing the Bay of Bengal can pick up moisture before reaching Tamil Nadu. This links the retreating monsoon season with the north-east monsoon circulation; the two labels describe closely related parts of the seasonal change.

Northern land cools → Summer monsoon retreats → Low-pressure belt moves south → North-easterlies cross the Bay of Bengal → Winds gain moisture → Tamil Nadu coast receives autumn rain

Why the others are wrong

(a) The winter (north-east) monsoon is the usual textbook name for this rain.

(c) There is no north-west monsoon here.

The trap

The season is called the retreating monsoon season; the rain-bearing circulation is commonly called the north-east monsoon. Read which aspect the wording tests.

Also know

Bay of Bengal depressions and cyclones can add intense rain during this season. The Coromandel coast faces the Bay, unlike the Malabar coast, which receives its main rain from summer Arabian Sea winds. Sri Lanka also receives north-east monsoon rain.