These winds blow on the equatorial side of the counterclockwise circulation of air that exists around the area of high pressure situated in about latitude 30 °S. Compared to the other oceans, the South Indian high rarely consists of a single cell and often contains a succession of east moving anticy-clonic systems. The trade winds blow on their north side and form a wide belt that stretches across the ocean from Western Australia to Madagascar and the coast of Africa. Between July and September this belt spreads over a very large area and becomes continuous with the SE trade winds of the South Pacific. The entire belt moves north and south throughout the year, its northern limit varying from latitude 2°S in August to latitude 12°S in January. The fluctuation of the southern limit is less pronounced, from 24°S in August to 30°S in January.
The average strength of these trade winds is between 10 and 15 knots in summer and 15 to 20 knots in winter. Over the central region, the wind blows steadily from SE or ESE, especially from May to September when the SW monsoon is in force north of the equator.
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