Tropical Cyclone Scales - Wind Speed Conversions

Wind Speed Conversions

The definition of sustained winds recommended by the World Meteorological Organization (WMO), and used by most weather agencies, is that of a 10-minute average at a height of 10 m (33 ft). However, RSMC Miami and RSMC Honolulu, as well as the Joint Typhoon Warning Center, define sustained winds based on 1-minute average speed (also measured 10 m (33 ft) above the surface).

Studies have shown that the two definitions are correlated, with the cyclone's maximum one-minute wind speed conventionally about 14% higher than its best ten-minute one. (To convert from a one-minute wind speed to a ten-minute wind speed, the one-minute speed is multiplied by 0.88. In the other direction, the ten-minute wind speed is multiplied by 1.14 to produce the one-minute wind speed.) This relationship is approximate, as the conversion factor varies with different land or sea surfaces and atmospheric stability.