How are Australian cyclones named and categorised?
The Bureau names every cyclone from rotating alphabetical lists and grades it 1–5 on wind gusts — here is how the system works and what the category leaves out.
The Bureau of Meteorology names every tropical cyclone in the Australian region from pre-approved alphabetical lists that alternate between male and female names, and it grades each storm on a five-tier intensity scale. Categories 1 to 5 are based on the strongest wind gusts — from Category 1 gales up to Category 5 gusts above 280 km/h. The category describes wind, not rain or storm surge.
Who names Australian cyclones?
The Bureau of Meteorology is the official Regional Specialised Meteorological Centre for the Australian region, which spans the ocean from 90°E to 160°E. When a tropical low intensifies to gale-force winds near its centre, BOM assigns it the next name from its lists. Australia has a long history here: meteorologist Clement Wragge was naming tropical systems around Queensland as early as the 1890s, making Australia one of the first places on Earth to give cyclones names.
How does the Bureau choose a name?
BOM maintains rotating alphabetical lists of names that alternate male and female. Names are chosen to be short, easy to pronounce and unlikely to cause offence. The public can even suggest names for the Bureau's future lists. A few rules shape how they are used:
- Names are assigned in strict order as new cyclones form — there is no skipping to a "better" name.
- Letters that yield too few usable names (such as Q, U, X, Y and Z) are generally not used.
- The name of any cyclone that causes significant death or damage is retired and never reused — which is why names like Tracy (Darwin, 1974) and Yasi (2011) will not return.
Because the Australian region sits in the Southern Hemisphere, the cyclone season runs roughly from November to April, opposite to the Northern Hemisphere's June-to-November hurricane season.
What do the cyclone categories mean?
Australia uses its own five-category intensity scale. The category is set by the maximum wind gust expected near the centre, with the sustained (10-minute mean) wind shown alongside. Here is the Bureau's scale:
| Category | Strongest gust | Mean (10-min) wind | Typical effect |
|---|---|---|---|
| 1 | Less than 125 km/h | 63–88 km/h | Gales; minor damage to crops, trees, caravans |
| 2 | 125–164 km/h | 89–117 km/h | Destructive winds; minor house damage, power loss |
| 3 | 165–224 km/h | 118–159 km/h | Very destructive; roof and structural damage |
| 4 | 225–279 km/h | 160–199 km/h | Significant roofing and structural damage; caravans destroyed |
| 5 | More than 280 km/h | More than 200 km/h | Extremely dangerous; widespread destruction |
Why is the Australian scale different from the American one?
This trips up a lot of people who follow US hurricanes. The American Saffir–Simpson scale is based on 1-minute sustained winds, while the Australian scale references 10-minute mean winds and headlines the strongest gust. Because a 1-minute average will always read higher than a 10-minute average of the same storm, the numbers do not line up one-for-one. An Australian Category 2 is not the same as an American Category 2. When comparing storms across basins, always check which scale is being used.
What happens after a cyclone crosses the coast?
A cyclone does not simply switch off at landfall. Cut off from the warm ocean that fuels it, the system weakens and is eventually reclassified as an ex-tropical cyclone or tropical low — but the danger can persist for days. The circulation drags tropical moisture far inland, and the heaviest, most damaging rainfall often falls after the winds have eased, sometimes hundreds of kilometres from where the eye came ashore. Rivers that were dry can rise to major flood levels well after the storm has "passed". This is why the Bureau keeps issuing flood warnings long after a cyclone has been downgraded, and why residents inland should watch a coastal cyclone closely even if they are nowhere near the coast.
How does the Bureau forecast a cyclone's track?
Tropical cyclone forecasting has improved dramatically, but it remains genuinely uncertain, especially several days out. The Bureau publishes a track map showing the forecast path and, crucially, a shaded uncertainty zone around it — the area the centre could reasonably reach. That cone is not a mistake or padding; it is an honest statement that the exact landfall point is not yet knowable. Track forecasts are typically more reliable than intensity forecasts, because predicting exactly how strong a cyclone will get involves small-scale processes that are hard to model. Read both the line and the shaded zone, and never assume a town just outside the cone is safe.
What does the category NOT tell you?
A cyclone's category describes wind only. It says nothing about the two hazards that often cause the most harm:
- Storm surge — the wall of seawater pushed ashore, driven by the storm's size and the coastline's shape as much as its wind.
- Flooding rain — a slow-moving, "lower-category" cyclone can dump catastrophic rainfall inland long after landfall.
A weakening Category 1 that stalls over a catchment can be far deadlier than a fast-moving Category 3 that clears quickly. Read the whole warning, not just the number.
How does checkweather track a cyclone?
The Bureau issues the official track and category, and we always link to it — BOM is the authority for Australian waters. What checkweather adds is a side-by-side view of how the global models see the same storm. When ECMWF, NOAA's GFS and DWD's ICON cluster tightly around one track, our forecast confidence score is high; when they fan out into a wide "spaghetti" spread days ahead, confidence is low and the landfall point is genuinely uncertain. Our accuracy scoreboard then grades each model against where the cyclone actually went. It is the plain-English version of the uncertainty that professional forecasters watch every day.