Warm waters are necessary to fuel the heat engine of the tropical cyclone.
An atmosphere which cools fast enough with height such that it is potentially unstable. It is the thunderstorm activity which allows the heat stored in the ocean waters to be liberated for the tropical cyclone development. Relatively moist layers near the mid-troposphere. Dry mid levels do not allow the continuing development of widespread thunderstorm activity. Tropical cyclones cannot be generated spontaneously.