1911 Encyclopædia Britannica/V-shaped Depression
V-shaped Depression, in meteorology, a narrow area of low pressure usually occurring between two adjacent anticyclones, and taking the form of a V or tongue, as do the isobars representing it on a weather-chart. Such a depression may be regarded as a projection from a cyclonic system lying to one side of the two anticyclones. A similar depression, however, is frequently formed within a larger area of depression, i.e. an ordinary cyclone, and sometimes develops so far as to have a complete circulation of its own; it is then known as a “ secondary.” The line of lowest depression following the axis of the V brings with it heavy squalls and a sudden change of wind from one direction almost to the opposite. It is preceded by signs of break in the weather such as usually herald the approach of an ordinary cyclone, and is followed by the usual signs of clearance. The occurrence of a V-depression or secondary within an ordinary cyclonic system intensifies, often to a dangerous degree, the usual disturbances in the weather accompanying that system. Conditions exactly opposite to those accompanying a V-shaped depression are provided by a “ wedge.” (q.v.).