Tropical Cyclones vs. Hurricanes vs. Major Hurricanes

What is the difference between a tropical cyclone, a hurricane, and a major hurricane?

A tropical cyclone is a warm-core low pressure system, without any front attached, that develops over the tropical or subtropical waters and has an organized circulation.¹

Within 5° latitude of the equator, the Coriolis force is insufficient to generate the ‘spin’ that is characteristic of cyclones.

Tropical cyclones forming in the North Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea basin (light-green area in Figure 1) have the potential to be classed as hurricanes.

Whether they are or not depends on the maximum sustained windspeed of the cyclone. If the maximum windspeed, sustained for periods of 1 minute or more, is at least 74 mph, then the tropical cyclone is classed as a ‘hurricane’.

The Saffir-Simpson Hurricane Wind Scale was developed to grade hurricanes by their damage potential.²

Hurricanes in category 3 and above (sustained windspeeds of 111 mph and above) are classed as major hurricanes(*).

Table 1. The Saffir-Simpson Hurricane Wind Scale.

Cat	Windspeed	Impact illustration: effect on trees
1	74-95 mph	Large branches of trees will snap; shallow-rooted trees can be toppled.
2	96-110 mph	Many shallowly rooted trees will be snapped or uprooted, blocking numerous roads.
3*	111-129 mph	Many trees will be snapped or uprooted, blocking numerous roads.
4*	130-156 mph	Most trees will be snapped or uprooted; power poles downed. Fallen trees and power poles will isolate residential areas.
5*	>156 mph	Nearly all trees will be snapped or uprooted and power poles downed. Fallen trees and power poles will isolate residential areas.

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