Wind Speed Scales
変換元 Gentle Breeze to Hurricane Force
Understand Wind CategoriesWeather reports mention "25 mph winds" or "Category 3 hurricane" or "gale force conditions." 理解する wind speed scales helps you interpret forecasts, prepare for storms, and appreciate the power of moving air—from the gentlest breeze to devastating hurricanes.
The Beaufort Wind Scale
Developed in 1805 by Sir Francis Beaufort for naval use, this scale correlates wind speed with observed sea and land conditions.
| Force | Name | MPH | KM/H | Knots | Effects |
|---|---|---|---|---|---|
| 0 | Calm | 0-1 | 0-2 | 0-1 | Smoke rises vertically |
| 1 | Light air | 1-3 | 2-6 | 1-3 | Smoke drifts |
| 2 | Light breeze | 4-7 | 7-11 | 4-6 | Leaves rustle |
| 3 | Gentle breeze | 8-12 | 12-19 | 7-10 | Flags extend |
| 4 | Moderate breeze | 13-18 | 20-29 | 11-16 | Small branches move |
| 5 | Fresh breeze | 19-24 | 30-39 | 17-21 | Small trees sway |
| 6 | Strong breeze | 25-31 | 40-50 | 22-27 | Umbrellas difficult |
| 7 | Near gale | 32-38 | 51-61 | 28-33 | Walking hindered |
| 8 | Gale | 39-46 | 62-74 | 34-40 | Twigs break |
| 9 | Strong gale | 47-54 | 75-87 | 41-47 | Minor structural damage |
| 10 | Storm | 55-63 | 88-102 | 48-55 | Trees uprooted |
| 11 | Violent storm | 64-72 | 103-117 | 56-63 | Widespread damage |
| 12 | Hurricane | 73+ | 118+ | 64+ | Devastating damage |
Saffir-Simpson Hurricane Scale
Used for Atlantic and Eastern Pacific hurricanes. Based on sustained wind speed.
| Category | MPH | KM/H | Knots | Damage Potential |
|---|---|---|---|---|
| 1 | 74-95 | 119-153 | 64-82 | Minimal: some roof/siding damage |
| 2 | 96-110 | 154-177 | 83-95 | Moderate: major roof damage, trees uprooted |
| 3 | 111-129 | 178-208 | 96-112 | Extensive: devastating damage, electricity out for days |
| 4 | 130-156 | 209-251 | 113-136 | Extreme: severe damage, areas uninhabitable for weeks |
| 5 | 157+ | 252+ | 137+ | Catastrophic: total destruction of many buildings |
Category 3-5 are considered "major hurricanes."
変換先rnado Scales
Enhanced Fujita (EF) Scale
| Rating | MPH | KM/H | Damage Description |
|---|---|---|---|
| EF0 | 65-85 | 105-137 | Light: branches broken, shingles damaged |
| EF1 | 86-110 | 138-177 | Moderate: mobile homes overturned, roofs stripped |
| EF2 | 111-135 | 178-217 | Significant: roofs torn off, large trees uprooted |
| EF3 | 136-165 | 218-266 | Severe: entire stories destroyed, heavy cars thrown |
| EF4 | 166-200 | 267-322 | Devastating: well-built homes leveled |
| EF5 | 200+ | 322+ | Incredible: strong buildings destroyed, cars missiles |
Other Wind Classifications
National Weather Service Terms
| Term | Wind Speed |
|---|---|
| Wind Advisory | Sustained 31-39 mph or gusts 46-57 mph |
| High Wind Warning | Sustained 40+ mph or gusts 58+ mph |
| Extreme Wind Warning | Sustained 115+ mph |
| Tropical Storm | 39-73 mph |
| Hurricane | 74+ mph |
Marine Terms
| Term | Knots | MPH |
|---|---|---|
| Small Craft Advisory | 18-33 | 21-38 |
| Gale Warning | 34-47 | 39-54 |
| Storm Warning | 48-63 | 55-73 |
| Hurricane Force Warning | 64+ | 74+ |
Measuring Wind Speed
Instruments
- Anemometer: Rotating cups measure wind speed
- Wind vane: Points into the wind for direction
- Doppler radar: Measures wind remotely
- Weather balloon: Upper atmosphere measurements
Sustained vs Gusts
- Sustained wind: Average over 1-2 minutes
- Gusts: Brief increases lasting seconds
Gusts typically exceed sustained winds by 30-50%.
まとめ
Wind speed scales translate abstract numbers into meaningful descriptions of conditions and hazards. The Beaufort scale covers everyday winds from calm to hurricane force. The Saffir-Simpson scale categorizes tropical storms by damage potential. 理解する these scales helps you prepare for weather events and interpret forecasts accurately.