The longevity of tropical-cyclone vortices after extratropical transition

Recent case studies of Atlantic hurricanes which transformed into extratropical storms have shown that such systems can cross the Atlantic and still have hurricane-like properties (for example, a tower of high potential vorticity extending through the troposphere). This paper addresses the question as to how long a tropical cyclone vortex can survive under the influence of surface friction and in the absence of convection. Examples will be presented of the structure of ex-hurricanes in the eastern Atlantic. The spin down of a tropical cyclone vortex in an axisymmetric model for a variety of parameters will be described.