A tropical cyclone, however, has a diameter on the scale of miles and is comprised of several to dozens of convective storms. Tornadoes are primarily an over-land phenomena as solar heating of the land surface usually contributes toward the development of the thunderstorm that spawns the vortex. Lastly, tropical cyclones have a lifetime that is measured in days, while tornadoes typically last on the scale of minutes. A hurricane needs several different factors present in order for it to develop. Warm ocean waters of at least 80 F throughout a sufficient depth of at least 150 ft.
Warm waters are necessary to fuel the heat engine of the tropical cyclone.
An atmosphere which cools fast as the elevation increases. This causes instability in the accumulation of moisture. Dry mid levels are not conducive for allowing the continuing development of widespread thunderstorm activity. Tropical cyclones cannot be generated spontaneously. To develop, they require a weakly organized system with sizable spin and low level inflow.