Reckoning / Weather / Tropical cyclones
Weather · basins and scale
Tropical cyclones
The same storm is a hurricane, a typhoon or a cyclone depending on the ocean. They form over warm water away from the equator, where the Earth’s rotation can set the air spinning; they almost never cross the equator.
Basins (approximate)
Basins and seasons
| Basin | Called | Season | Peak | |
|---|---|---|---|---|
| 1 | North Atlantic | hurricane | 1 June to 30 November (official) | September |
| 2 | Eastern North Pacific | hurricane | 15 May to 30 November | August to September |
| 3 | Western North Pacific | typhoon | all year | August to September |
| 4 | North Indian Ocean | cyclonic storm | April to June and October to December | May and November |
| 5 | South-West Indian Ocean | tropical cyclone | November to April | January to March |
| 6 | Australian region | tropical cyclone | November to April | January to March |
| 7 | South Pacific | tropical cyclone | November to April | February to March |
Sources: Tropical cyclone FAQ: basins, names and seasons; map: Natural Earth 1:110m land (public domain), via world-atlas 2.0.2. The boxes mark the main breeding grounds, not official boundaries.
Saffir–Simpson hurricane wind scale
| Category | Wind, knots | km/h |
|---|---|---|
| 1 | 64–82 | 119–153 |
| 2 | 83–95 | 154–177 |
| 3 | 96–112 | 178–208 |
| 4 | 113–136 | 209–251 |
| 5 | 137+ | 252+ |
One-minute sustained wind. Source: Saffir-Simpson Hurricane Wind Scale. A hurricane begins at 64 knots, Beaufort force 12.
Older charts drew storm tracks as hand-sketched average paths. Today each basin has a regional centre that names storms and issues warnings, and decades of satellite tracks show where they really go.