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A wind gust or just gust is a brief, sudden increase in the wind speed. It usually lasts for less than 20 seconds, briefer than a squall, which lasts minutes. A gust is followed by a lull (or slackening) in the wind speed. [1] Generally, winds are least gusty over large water surfaces and most gusty over rough land and near high buildings. [2]
Wind speed on the Beaufort scale is based on the empirical relationship: [6] v = 0.836 B 3/2 m/s; v = 1.625 B 3/2 knots (=) where v is the equivalent wind speed at 10 metres above the sea surface and B is Beaufort scale number.
In Canada, reference wind pressures are used in design and are based on the "mean hourly" wind speed having a probability of being exceeded per year of 1 in 50. The reference wind pressure q is calculated using the equation q = ρv 2 / 2 , where ρ is the air density and v is the wind speed.
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 by 10 knots (19 km/h; 12 mph) for periods of seconds. A squall is an increase of the wind speed above a certain threshold, which lasts for a minute or more.
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. For example, Hurricane Sandy had a lower pressure than expected with its associated wind speed. [7]
In common usage, wind gradient, more specifically wind speed gradient [1] or wind velocity gradient, [2] or alternatively shear wind, [3] is the vertical component of the gradient of the mean horizontal wind speed in the lower atmosphere. [4] It is the rate of increase of wind strength with unit increase in height above ground level.
Wind measuring has been standardized globally to reflect the winds at 10 metres (33 ft) above mean sea level, [nb 1] and the maximum sustained wind represents the highest average wind over either a one-minute (US) or ten-minute time span (see the definition, below), anywhere within the tropical cyclone. Surface winds are highly variable due to ...
High wind watch HWA – Strong sustained winds of 40 to 73 miles per hour (64 to 117 km/h) or greater for one hour or more, or wind gusts of 58 to 89 miles per hour (93 to 143 km/h) for any duration are expected within 12 to 48 hours. Wind speeds may pose a hazard to pedestrian and vehicular travel (including toppling or creating flying debris ...