The roles of ENSO on the occurrence of abruptly recurving tropical cyclones over the Western North Pacific Ocean Basin

The quasi-periodic El Ni o -Southern Oscillation (ENSO) phenomenon in the tropical Pacific Ocean produces the largest interannual variation in the cold season climate of Canada. The diabatic heating in the eastern tropical Pacific, associated with the warm phase of ENSO (El Ni o), triggers Rossby waves which in turn gives rise to the Pacific-North American teleconnection (PNA) over the North American sector. The strongest cell of the PNA pattern lies over western Canada. In most of southern Canada, mean winter temperature distribution is shifted towards warmer values, and precipitation is below normal. The presence of El Ni o provides the best opportunity to make skillful long-range winter forecast for Canada. A strong El Ni o event, while bringing respite from the otherwise cold winter in Canada, can be expected to cost the Canadian economy two to five billion dollars.