Extratropical Cyclone
Any cyclone that is no longer tropical in origin. Generally considered to be a migratory frontal cyclone found in the middle and high latitudes. An extratropical storm is a cyclone that no longer derives its energy source from the processes involved in sustaining a tropical cyclone, but thrives on baroclinic processes; i.e., the temperature contrast between warm and cold air masses. The term extratropical is typically used when a tropical cyclone moves away from the tropics and moves poleward into cooler waters thus losing its tropical characteristics.
Cyclone
An area of closed pressure circulation with rotating and converging winds, the center of which is a relative pressure minimum. The circulation is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Also called a low pressure system and the term used for a tropical cyclone in the Indian Ocean. Other phenomena with cyclonic flow may be referred to by this term, such as dust devils, tornadoes, and tropical and extratropical systems. The opposite of an anticyclone or a high pressure system.
Tropics / Tropical
The region of the earth located between the Tropic of Cancer, at 23.5 degrees North latitude, and the Tropic of Capricorn, at 23.5 degrees South latitude. It encompasses the equatorial region, an area of high temperatures and considerable precipitation during part of the year.
Middle Latitudes
The latitude belt roughly between 35 and 65 degrees North and South. May be referred to as the temperate region.
High Latitudes
The latitude belt roughly between 60° and 90° North and South.