Frequently Asked Questions (FAQ)

Climatology | Impacts | Extremes| TCs affecting WA towns | Forecast Accuracy
Frequently Asked Questions | Annual summaries

Definitions | Characteristics and Formation | Climatology | Extremes | Forecasting | More Information

Definitions

5. How are tropical cyclones different from tornadoes?

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 usually produced from a single thunderstorm. A tropical cyclone, however, has a diameter on the scale of hundreds of kilometers and contains many thunderstorms. 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 (though over-water tornadoes have occurred). In contrast, 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.

Interestingly, tropical cyclones near landfall often provide the conditions necessary for tornado formation. As the strong onshore surface winds move over land they weaken, but above the surface (> 1 km) winds are not affected. This creates strong wind shear that is conducive to tornado formation, especially on the cyclone's left forward quadrant (in the southern hemisphere). It is believed that most of the tornadoes that do form occur in the outer rainbands some 80-300 km from the centre, but some have been documented to occur in the inner core of the eye wall. It is possible that the extreme damage produced from winds in the eye wall are actually due to tornadoes.