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The Australian Bureau of Meteorology uses a 1-5 scale called tropical cyclone severity categories . Unlike the Saffir-Simpson Scale, severity categories are based on strongest wind gusts and not sustained winds. Severity categories are scaled somewhat lower than the Saffir-Simpson Scale, with a severity category 2 tropical cyclone being roughly equivalent to a Saffir-Simpson category 1 hurricane.
The initial scale was developed by Saffir while on commission from the United Nations to study low-cost housing in hurricane-prone areas. While performing the study, Saffir realized there was no simple scale for describing the likely effects of a hurricane. Knowing the utility of the Richter magnitude scale in describing earthquakes, he devised a 1–5 scale based on wind speed that showed expected damage to structures. Saffir gave the scale to the NHC, and Simpson added in the effects of storm surge and flooding.
The five categories are, in order of increasing intensity:
| Category 1 | Sustained winds | 74–95 mph | 64–82 kt. | 119–153 km/h |
|---|---|---|---|---|
| Storm surge | 4–5 ft. | 1.2–1.5 m | ||
| Central pressure | 28.94 in HgPressure (symbol: p is a measure of force per unit area. where p is the pressure F is the force A is the area Often F is taken to be the of the magnitude of the mean vector force normal to the surface of area A upon which it exerts; the "surface" not nece | 980 mbA millibar is 1/1000th of a bar metric unit for measurement of pressure. It is not an SI unit of measure. The SI unit is the pascal (Pa), with 1 millibar 100 pascals. The millibar unit was introduced by Sir Napier Shaw in 1909, and internationally adopted | ||
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| Example storms | Hurricane Agnes | |||
| Category 2 | Sustained winds | 96–110 mph | 83–95 kt. | 154–177 km/h |
| Storm surge | 6–8 ft. | 1.8–2.4 m | ||
| Central Pressure | 28.50–28.91 in Hg | 965–979 mb | ||
| Potential damage | Some roofing material, door, and window damage. Considerable damage to vegetation, mobile homes, etc. Flooding damages piers and small craft in unprotected moorings may break their moorings. | |||
| Example storms | Hurricane Diane – Hurricane Juan | |||
| Category 3 | Sustained winds | 111–130 mph | 96–113 kt. | 178–209 km/h |
| Storm surge | 9–12 ft. | 2.7–3.7 m | ||
| Central pressure | 27.91–28.47 in Hg | 945–964 mb | ||
| Potential damage | Some structural damage to small residences and utility buildings, with a minor amount of curtainwall failures. Mobile homes are destroyed. Flooding near the coast destroys smaller structures with larger structures damaged by floating debris. Terrain may be flooded well inland. | |||
| Example storms | Hurricane Fran – Hurricane Isidore – Hurricane Jeanne | |||
| Category 4 | Sustained winds | 131–155 mph | 114–135 kt. | 210–249 km/h |
| Storm surge | 13–18 ft. | 4.0–5.5 m | ||
| Central pressure | 27.17–27.88 in Hg | 920–944 mb | ||
| Potential damage | More extensive curtainwall failures with some complete roof structure failure on small residences. Major erosion of beach areas. Terrain may be flooded well inland. | |||
| Example storms | Galveston Hurricane of 1900 – Hurricane Hugo – Hurricane Iris – Hurricane Charley | |||
| Category 5 | Sustained winds | ≥156 mph | ≥136 kt. | ≥250 km/h |
| Storm surge | ≥18 ft. | ≥5.5 m | ||
| Central pressure | <27.17 in Hg | <920 mb | ||
| Potential damage | Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. Flooding causes major damage to lower floors of all structures near the shoreline. Massive evacuation of residential areas may be required. | |||
| Example storms | Hurricane Camille – Hurricane Gilbert – Hurricane Andrew | |||
All wind speeds are based on a one-minute average. Central pressure values are approximate. Intensity of example hurricanes is at time of landfall.