What are the Australian tropical cyclone categories?

April 06, 2006 - 03:09 PM UTC

Like the Saffir-Simpson scale used in the United States, the Australian cyclone severity index rates storms on a scale from 1 (weakest) to 5 (strongest) based on the maximum sustained winds. However, the Australian scale is created for weaker storms. Below is a table from the Australian Bureau of Meteorology explaining their scale:

Category Strongest Gust (km/h) Average Maximum Wind (km/h) Approximate Central Pressure (hPa) Typical Effects
1 < 125 63 - 88 > 985 Negligible house damage. Damage to some crops, trees and caravans. Craft may drag moorings
2 125 - 169 89 - 117 985 - 970 Minor house damage. Significant damage to signs, trees and caravans. Heavy damage to some crops. Risk of power failure. Small craft may break moorings.
3 170 - 224 118 - 159 970 - 955 Some roof and structural damage. Some caravans destroyed. Power failures likely. (e.g. Winifred)
4 225 - 279 160 - 199 955 - 930 Significant roofing loss and structural damage. Many caravans destroyed and blown away. Dangerous airborne debris. Widespread power failures. (e.g. Tracy, Olivia)
5 > 279 > 200 < 930 Extremely dangerous with widespread destruction. (e.g. Vance)

Below is another table from the Australian Bureau of Meteorology comparing the US Saffir-Simpson scale to the Australian cyclone severity scale.

10-min av. wind speed (knots) 1-min av. wind speed (kn) USA Category Australian Category Wind gusts (km/h) Wind gusts (kn)
57 65 Category 1 Category 2 148 80
61 70 157 85
65 75 169 91
70 80   181 98
74 85 Category 2   193 104
78 90 Category 3 202 109
83 95   215 116
87 100 Category 3   226 122
91 105   235 127
96 110 Category 4 248 134
100 115 Category 4   259 140
105 120   272 147
109 125 Category 5 283 153
113 130 293 158
118 135 306 165
122 140 Category 5 317 171
126 145 326 176
131 150 339 183

Posted by Bryan Woods