A Cut-Off Low (COL) is a low pressure system that develops south of South Africa, stemming from the main westerly trough systems of cold air. As the COL develops, it deepens into a defined closed system that extends from the upper air downward to the surface of the earth. A COL system usually prevails over an area for more than a day , and can last for up to 6 days. The COL moves slowly over a confined region leading to extreme rainfall. COL’s are unstable, baroclinic systems that slope to the west with height and are associated with strong convergence and upward motion, particularly while they are deepening.
Typical Synoptic sequence and weather associated with a Cut-Off Low