In meteorology, a cyclone refers to any low pressure area with winds spiralling inwards. Cyclones rotate clockwise in the Southern Hemisphere and anti-clockwise in the Northern Hemisphere. Cyclone is the general term for a variety of low pressure system types, such as tropical cyclones, extra tropical cyclones and tornadoes.
The largest of the low-pressure systems are the extratropical cyclones and the cold-core polar cyclones which lie on the synoptic scale which in meteorology is a horizontal length of 1000 km or more. The Warm-core cyclones are the tropical cyclones, mesocyclones, and the polar lows that lie within the smaller mesoscale. The Subtropical cyclones are intermediate in size. Cyclones have also been on other planets outside of the Earth, such as Mars and Neptune. For example the Great Red Spot of Jupiter and the Great Black Spot of Neptune.
Cyclones are also referred to as hurricanes and typhoons. They consist of the eye, eyewall and rainbands.
The process of cyclone formation and intensification is described as Cyclogenesis. The formation of Extratropical cyclones comes as waves in large regions of enhanced midlatitude temperature contrasts which are called baroclinic zones. These zones contract to form weather fronts as the circulation of the cyclone closes and gets more intense. Later in their life cycle, cyclones form what is called an occluded front. The cyclone's track is then guided over the course of an 2 to 6 day life cycle by its steering flow of the polar or subtropical jetstream.
- Media related to Astronaut images of tropical cyclones at Wikimedia Commons