Extreme Precipitation Associated with Extratropical Transition

A number of documented cases of heavy precipitation associated with hurricanes in transition to extratropical (ET), suggests that some of the costliest natural disasters in Canada and the USA are associated with this phenomena. Indeed, extreme rainfalls associated with storms like the 1938 hurricane, Agnes in 1972, and Hazel in 1954, are relatively well known. However, recent research suggests that this transition process is responsible for potentially many more significant events that have not been recognized as being associated with extra-tropical transition. Indeed, there is evidence that this process contributed to the very heavy rainfalls associated with "Floyd" in 1999. This paper will discuss a number of these cases, along with their characteristics that allow for the development of a conceptual forecast model useful for operational prediction.