Wind Force Scale
See also: Tropical cyclone scales and Surface weather analysisHistorically, the Beaufort wind force scale provides an empirical description of wind speed based on observed sea conditions. Originally it was a 13-level scale, but during the 1940s, the scale was expanded to 17 levels. There are general terms that differentiate winds of different average speeds such as a breeze, a gale, a storm, tornado, or a hurricane. Within the Beaufort scale, gale-force winds lie between 28 knots (52 km/h) and 55 knots (102 km/h) with preceding adjectives such as moderate, fresh, strong, and whole used to differentiate the wind's strength within the gale category. A storm has winds of 56 knots (104 km/h) to 63 knots (117 km/h). The terminology for tropical cyclones differs from one region to another globally. Most ocean basins use the average wind speed to determine the tropical cyclone's category. Below is a summary of the classifications used by Regional Specialized Meteorological Centers worldwide:
| General wind classifications | Tropical cyclone classifications (all winds are 10-minute averages) | |||||||
|---|---|---|---|---|---|---|---|---|
| Beaufort scale | 10-minute sustained winds (knots) | General term | N Indian Ocean IMD |
SW Indian Ocean MF |
Australian region South Pacific BoM, BMKG, FMS, MSNZ |
NW Pacific JMA |
NW Pacific JTWC |
NE Pacific & N Atlantic NHC & CPHC |
| 0 | <1 | Calm | Low Pressure Area | Tropical disturbance | Tropical low Tropical Depression |
Tropical depression | Tropical depression | Tropical depression |
| 1 | 1–3 | Light air | ||||||
| 2 | 4–6 | Light breeze | ||||||
| 3 | 7–10 | Gentle breeze | ||||||
| 4 | 11–16 | Moderate breeze | ||||||
| 5 | 17–21 | Fresh breeze | Depression | |||||
| 6 | 22–27 | Strong breeze | ||||||
| 7 | 28–29 | Moderate gale | Deep depression | Tropical depression | ||||
| 30–33 | ||||||||
| 8 | 34–40 | Fresh gale | Cyclonic storm | Moderate tropical storm | Tropical cyclone (1) | Tropical storm | Tropical storm | Tropical storm |
| 9 | 41–47 | Strong gale | ||||||
| 10 | 48–55 | Whole gale | Severe cyclonic storm | Severe tropical storm | Tropical cyclone (2) | Severe tropical storm | ||
| 11 | 56–63 | Storm | ||||||
| 12 | 64–72 | Hurricane | Very severe cyclonic storm | Tropical cyclone | Severe tropical cyclone (3) | Typhoon | Typhoon | Hurricane (1) |
| 13 | 73–85 | Hurricane (2) | ||||||
| 14 | 86–89 | Severe tropical cyclone (4) | Major hurricane (3) | |||||
| 15 | 90–99 | Intense tropical cyclone | ||||||
| 16 | 100–106 | Major hurricane (4) | ||||||
| 17 | 107–114 | Severe tropical cyclone (5) | ||||||
| 115–119 | Very intense tropical cyclone | Super typhoon | ||||||
| >120 | Super cyclonic storm | Major hurricane (5) | ||||||
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