This picture taken in August 1992 shows the wind patterns in the
Indian Ocean that permitted ocean travel at regular intervals. North
of the equator north-east winds prevail in the winter and south of
the equator north-west winds predominate. During the rest of the year
winds blow steadily from the south and west.
If you have a few extra minutes and want to see what the winds were like in the Indian Ocean yesterday see Indian Ocean Winds (P.S. You need Quick Time a free viewer to see the patterns. But it is worth it!)