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 (roaring forties). They are associated with the strong pressure gradient on the equatorial side of the frequent depressions passing eastward in sub-polar temperate latitudes; hence they fluctuate mainly between southwest and northwest.