A gale is a strong wind, typically used as a descriptor in nautical contexts. The U.S. National Weather Service defines a gale as 34–47 knots (63–87 km/h, 17.5–24.2 m/s or 39–54 miles/hour) of sustained surface winds. Forecasters typically issue gale warnings when winds of this strength are expected. In the United States, a gale warning is specifically a maritime warning; the land-based equivalent in National Weather Service warning products is a wind advisory.
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Other sources use minima as low as 28 knots (52 km/h; 14 m/s; 32 mph), and maxima as high as 90 knots (170 km/h; 46 m/s; 100 mph). Through 1986, the National Hurricane Center used the term gale to refer to winds of tropical force for coastal areas, between 33 knots (61 km/h; 17 m/s; 38 mph) and 63 knots (117 km/h; 72 mph; 32 m/s). The 90 knots (170 km/h; 46 m/s; 100 mph) definition is very non-standard. A common alternative definition of the maximum is 55 knots (102 km/h; 63 mph; 28 m/s).
The most common way of measuring wind force is with the Beaufort scale which defines a gale as wind from 50 kilometres per hour (14 m/s) to 102 kilometres per hour (28 m/s). It is an empirical measure for describing wind speed based mainly on observed sea conditions. On the original 1810 Beaufort wind force scale, there were four different "gale" designations whereas generally today there are two gale forces, 8 and 9, and a near gale 7:
|Wind force||Original name||Current name||km/h||m/s||mph||knots||Mean knots||Sea state|
|7||Moderate gale||Near gale||50–61||14–17||32–38||28–33||30||Rough–Very rough|
|8||Fresh gale||Gale||62–74||17–20||39–46||34–40||37||Very rough–High|
|9||Strong gale||Severe gale||75–88||21–24||47–54||41–47||44||High|
|10||Whole gale||Storm||89–102||25–28||55–63||48–55||52||Very High|