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The Saffir–Simpson hurricane wind scale (SSHWS) is a scale that classifies hurricanes—which in the Western Hemisphere are tropical cyclones that exceed the intensities of tropical depressions and tropical storms—into five categories distinguished by the intensities of their sustained winds.
The lowest official classification used in the North Indian Ocean is a depression, which has 3-minute sustained wind speeds of between 17 and 27 kn (20 and 31 mph; 31 and 50 km/h). [21] Should the depression intensify further then it will become a deep depression, which has winds between 28 and 33 kn (32 and 38 mph; 52 and 61 km/h). [ 21 ]
Direction shown by smoke drift but not by wind vanes 2 Light breeze 4–6 knots 4–7 mph 6–11 km/h 1.6–3.3 m/s 1–2 ft 0.3–0.6 m Small wavelets still short but more pronounced; crests have a glassy appearance but do not break Wind felt on face; leaves rustle; wind vane moved by wind 3 Gentle breeze 7–10 knots 8–12 mph 12–19 km/h
The interchangeability of pressure and wind allows for the two to be used to give equivalencies for the public. [7] Pressure-wind relations can be used when information is incomplete, forcing forecasters to rely on the Dvorak Technique. [6] Some storms may have particularly high or low pressures that do not match with their wind speed.
In most tropical cyclone basins, use of the satellite-based Dvorak technique is the primary method used to estimate a tropical cyclone's maximum sustained winds. [5] The extent of spiral banding and difference in temperature between the eye and eyewall is used within the technique to assign a maximum sustained wind and pressure. [6]
Roughness length is a parameter of some vertical wind profile equations that model the horizontal mean wind speed near the ground. In the log wind profile, it is equivalent to the height at which the wind speed theoretically becomes zero in the absence of wind-slowing obstacles and under neutral conditions. In reality, the wind at this height ...
Knowing the wind sampling average is important, as the value of a one-minute sustained wind is typically 14% greater than a ten-minute sustained wind. [16] A short burst of high speed wind is termed a wind gust ; one technical definition of a wind gust is: the maxima that exceed the lowest wind speed measured during a ten-minute time interval ...
Common developmental patterns seen during tropical cyclone development, and their Dvorak-assigned intensities. The Dvorak technique (developed between 1969 and 1984 by Vernon Dvorak) is a widely used system to estimate tropical cyclone intensity (which includes tropical depression, tropical storm, and hurricane/typhoon/intense tropical cyclone intensities) based solely on visible and infrared ...