1911 Encyclopædia Britannica/Roaring Forties

Roaring Forties, the name given to the zone in the southern hemisphere, near the 40th parallel of latitude, in which the north-westerly “anti-trade” winds attain their greatest development. Since the belt lies in the Great Southern Ocean (q.v.), and is little interrupted by land, the “planetary circulation” undergoes little modification and barometric gradients are steep. The “brave west winds” are accordingly of great strength, and, as in the corresponding belt of the northern hemisphere, the movement is largely broken up into the low and high pressure vortices known as cyclones and anticyclones.