Answer:
For the last few thousand years mariners, and the trade routes in the Indian Ocean have moved according th the rhythm based on seasonal weather patterns. They are known as monsoons.
The two main monsoons blow from the North East in the winter; and South West in the summer with a variable weather season in between.
Explanation:
The two monsoons have very different characteristics, despite the fact they take place over the same body of water The north-easterly monsoon of the winter is characterised by dry, steady, relatively gentle winds which encourage sailing throughout its duration. Meanwhile, the south-westerly summer monsoon is wet, violent and characterised by storms and strong wind with sailing only feasible at the beginning and end of the season.
Timing to connect with the right kind of winds was a determining factor for the voyage; and most traders preferred stopovers at focal points. Malacca the most obvious one.
