On average, about four tropical cyclones affect Atlantic Canada and its neighbouring marine waters each year. Many of these are in transition from tropical to extratropical, presenting a forecast challenge to meteorologists. Furthermore, the structural changes (e.g. wind and precipitation) and rapid accelerations in forward motion result in these storms posing a serious threat to life and property for both the marine and inland public communities.

Given the lack of scientific understanding of the structural evolution of tropical cyclones in the middle latitudes, the Meteorological Service of Canada in collaboration with the Canadian National Research Council (NRC), conducted two research aircraft flights into storms affecting Atlantic Canada. In October, 2000, the NRC Convair 580, equipped with cloud microphysical probes and a 35-GHz radar, dropped a series of dropsondes in and around Hurricane "Michael." Subsequently, in October 2001, a similar flight was flown into Tropical Storm "Karen."

This paper will present some of the very unique and interesting data collected during these investigations, and compare these data with the conceptual models that meteorologists have developed to assist in the diagnosis and prediction of extratropical transitions.