Another type of a subtropical cyclone is a mesoscale low forming in or near an area of horizontal wind shear, also known as a "dying frontal zone", with radius of strongest winds normally less than 30 miles (50 kilometers). The entire circulation may originally have a diameter of less than 100 miles/160 kilometres. These cyclones usually last for a short time. They may be either cold core or warm core, and for some time in 1972 this type of subtropical cyclone was called a "neutercane". As of 2006, the warm core type was moved under the definition of the term, tropical cyclone; and removed from the subtropical cyclone definition.