Just because he called them "tradewinds in another time" does not necessarily mean that the Aryth Ocean is the Atlantic Ocean. Tradewinds/Jet Stream are modern meterological terms used for the phenomena of wind moving across the face of a planet. Because we do not KNOW of any other weather forecasters from another planet, doesnt necessarily mean that there are NOT tradewinds on their planets. it is the movement of air from the east to the west which also controls the formation of tropical cyclones/hurricanes.

I liked it because it showed a comparison to something someone NOT in randland can use to relate to the movement of that wind across the surface of the ocean. The only thing that bugged me is Seanchan is in the WEST over the edge of the world so to speak, so they wouldn't be true tradewinds since those flow from East to west and NOT west to east. just my two cents