While both tropical cyclones and tornadoes are atmospheric vortices, they have little in common. Tornadoes have diameters on the scale of hundreds of meters and are produced from a single convective storm (i.e. a thunderstorm or cumulonimbus cloud). A tropical cyclone, however, has a diameter on the scale of hundreds of kilometers and is comprised of several to dozens of convective storms.

Additionally, while tornadoes require substantial vertical shear of the horizontal winds to provide ideal conditions for tornado genesis, tropical cyclones require very low values of tropospheric vertical shear in order to form and grow. Tornadoes are produced in regions of large temperature gradient, while tropical cyclones are generated in regions of near zero horizontal temperature gradient.

Also, tornadoes are primarily an over-land phenomenon, as solar heating of the land surface usually contributes toward the development of the thunderstorm that spawns the vortex, although over-water tornadoes have occurred. But tropical cyclones are purely an oceanic phenomena. They die out over land due to a loss of a moisture source.

Lastly, tropical cyclones have a lifetime that is measured in days, while tornadoes typically last on the scale of minutes.

Source: Atlantic Oceanographic and Meteorological Laboratory