This is a goofy explanation, but I hope it helps.

Find a sat photo of the Atlantic Ocean. I'd recommend Goes-8. You can view it best on a visible or water vapor loop. Just look for the general clockwise turning across most of the Atlantic (high pressure). Then look at the southern periphery of the high pressure. You will see some clouds (on the visible) pushing south at the Inter Tropical Convergence Zone (ITCZ) and surpressing the waves further toward the south.

Take a look and see if you get what I'm saying. If not, someone with a real [tm] explanation should be around by then.

Steve