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Subject: D2) How are Australian tropical cyclones ranked?
Cyclone Severity Categories - From the
Australian Bureau of Meteorology FAQ
An estimate of cyclone severity is now included in all
tropical cyclone advices. The table below provides information
concerning effects due to wind which are typical of cyclones in
the various categories. Remember that the system is not designed
to give an exact statement of conditions at individual locations
but will give a general idea of the expected worst conditions.
Categories of cyclone severity range from " 1 " for weak cyclones
to "5" for the most severe cyclones. Accordingly, the risk of
property and crop damage, shore erosion and danger to life
increases from low for a category 1 to very high for a category 5
cyclone. Using this severity scale, communities will be able to
assess the degree of cyclone threat and take appropriate action.
It must be emphasized that the category refers to the severity in
the zone of maximum winds and therefore the effects felt at
individual locations may not be exactly as described in the
accompanying table.
Damage will vary from location to location depending upon factors
such as:
- how far you are from the zone of maximum winds
- how exposed the location is
- building standards
- vegetation type
- resultant flooding
It should also be noted that the category does not refer to storm
tides; if a storm tide is expected it will be mentioned
separately in the cyclone warning.
Tropical Cyclone Severity
Categories |
Strongest Gusts |
Averaged Wind Speeds |
Typical effects (indicative only) |
Examples |
1 |
90 - 125 km/h |
63-88 km/h |
Negligible house damage. Damage to some crops, trees and
caravans. Craft may drag moorings. |
Cyclone Olga 2010 |
2 |
125 - 164 km/h |
89 - 117 km/h |
Minor house damage. Significant damage to signs, trees and
caravans. Heavy damage to some crops. Risk of power failure. Small craft
may break moorings. |
Cyclone Anthony 2011 |
3 |
165 - 224 km/h |
118 - 159 km/h |
Some roof and structural damage. Some caravans destroyed. Power
failure likely. |
Cyclone Magda 2010 |
4 |
225 - 279 km/h |
160 - 199 km/h |
Significant roofing loss and structural damage. Many caravans
destroyed and blown away. Dangerous airborne debris. Widespread power failure.
|
Cyclone Tracy 1974 & Cyclone Larry 2006 |
5 |
> 279 km/h |
> 200 km/h |
Extremely dangerous with widespread destruction. |
Cyclone Yasi 2011 |
Note: Average wind speed is for 10-minute average. 1 km/h ~
.54 kt or .63 mph
Last revised May 20, 2011
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