February 24, 2024

2 min

Skills & Seamanship

The Beaufort Scale

beaufort scale

The Beaufort Scale, a system for estimating wind strength based on observed sea conditions, was developed by Sir Francis Beaufort, an Irish-born British naval officer and hydrographer, in 1805. Beaufort’s initial motivation was to standardize the description of wind force at sea, which until then varied greatly and was often subjective. His scale ranged from 0 (calm) to 12 (hurricane) and was initially intended for use by sailors to describe wind effects on a fully rigged man-of-war, the typical naval vessel of the time.

In its original form, the Beaufort Scale was purely observational, relating wind speed to the sea’s surface conditions and the amount of sail a ship could carry. For example, “1” on the scale indicated a wind that could fill a ship’s sails, while “12” was a hurricane that would cause severe structural damage. Over the years, the Beaufort Scale evolved. Its usage extended beyond naval applications to include all maritime activities and even onshore observations. In the early 20th century, quantitative wind speeds were assigned to the Beaufort numbers. This allowed for more objective and consistent measurements across different contexts.

The scale also expanded to include descriptions of land conditions and effects on structures and vegetation, making it more universally applicable. Today, the Beaufort Scale remains an essential meteorological tool for weather observation and forecasting. It is a simple yet effective way to gauge wind intensity, both at sea and on land, and continues to be used by sailors, meteorologists, and weather enthusiasts worldwide.

ForceWindAppearance of Wind Effects
(Knots)ClassificationOn the Water
0< 1CalmSea surface smooth and mirror-like
11-3Light AirScaly ripples, no foam crests
24-6Light BreezeSmall wavelets, crests glassy, no breaking
37-10Gentle BreezeLarge wavelets, crests begin to break, scattered whitecaps
411-16Moderate BreezeSmall waves 1-4 ft. becoming longer, numerous whitecaps
517-21Fresh BreezeModerate waves 4-8 ft taking longer form, many whitecaps, some spray
622-27Strong BreezeLarger waves 8-13 ft, whitecaps common, more spray
728-33Near GaleSea heaps up, waves 13-19 ft, white foam streaks off breakers
834-40GaleModerately high (18-25 ft) waves of greater length, edges of crests begin to break into spindrift, foam blown in streaks
941-47Strong GaleHigh waves (23-32 ft), sea begins to roll, dense streaks of foam, spray may reduce visibility
1048-55StormVery high waves (29-41 ft) with overhanging crests, sea white with densely blown foam, heavy rolling, lowered visibility
1156-63Violent StormExceptionally high (37-52 ft) waves, foam patches cover sea, visibility more reduced
1264+HurricaneAir filled with foam, waves over 45 ft, sea completely white with driving spray, visibility greatly reduced
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