Gale

a wind of force 8 on the BEAUFORT SCALE (more than 30 knots).

Taken from Dictionary of Science

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A gale is a very strong wind. There are conflicting definitions of how strong. The U.S. Government's National Weather Service defines a gale as 34 to 47 knots (63 - 87 km/h or 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.

Other sources use minimums as low as 28 knots (52 km/h) and maximums as high as 90 knots (170 km/h). Through 1986, the National Hurricane Center used the term gale to refer to winds of tropical storm force for coastal areas, between 33 knots (61 km/h) and 63 knots (117 km/h). The 90-knot (170 km/h) definition is very non-standard. A common alternative definition of the maximum is 55 knots (102 km/h).

The most common way of measuring winds is with the Beaufort scale (pronounced /ˈboʊfət/). It is an empirical measure for describing wind speed based mainly on observed sea conditions. Its full name is the Beaufort wind force scale.

Taken from Wikipedia