What cold area do tropical disturbances have to survive through to then be rejuvenated by heat and moisture of the warmer water of the mid-atlantic?

Tropical disturbances that form over the warm waters of the mid-Atlantic, have to survive the cold waters on that come down south alongside the west coast of North America. These cold waters come down from Greenland, along the west coast of Canada and then west coast of USA. They bring cold air masses with them that are more dense, heavier, and break down the hurricanes, which is why they are very limited (most of the time) to the southwest of the USA and the Caribbean surrounding area. As they go further north they are becoming weaker and eventually break down.