A nautical term for the strong and rather persistent westerly winds over the oceans in temperate latitudes. They occur between latitudes 40° and 65° in the Northern Hemisphere and 35° to 65° in the Southern Hemisphere, where they are more regular and are strongest between 40° and 50°S (roaring forties). They are associated with the strong pressure gradient on the equatorial side of the frequent depressions passing eastward in subpolar temperate latitudes; hence they fluctuate mainly between southwest and northwest.