The Beaufort Scale

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The “Beaufort Scale” has been around in one form or another for over 200 years. Both mariners and landlubbers all around the world use the Scale to estimate wind speed in a standardized way. The Beaufort Scale was first devised in 1805 by Rear Admiral Sir Francis Beaufort, an Irish Royal Navy Officer. Many revisions were applied during the 19th century before the Scale evolved into its present form which contains 13 numbers or “forces” ranging from “0” (calm) to “12” (hurricane). The Scale’s endurance can be attributed to its utility, simplicity, and beauty. The language is descriptive but concise, vivid yet succinct, and poetic while also being very useful. Let us apply a recent local example by considering the maximum sustained winds observed during Tropical Storm Isaac (August 26–27). Maximum sustained winds at the automated weather stations atop the lighthouses along the Florida Reef tract were in the range of 40–45 knots. According to the Beaufort Scale, such winds would classify as “Force 9”, or “Strong Gale” (High waves; sea begins to roll; dense streaks of foam; spray may reduce visibility). Of course, such wind is the exception rather than the rule in the Florida Keys where average wind speeds for much of the year can be classified as Force 3 (“Gentle Breeze”; 7–10 knots) or Force 4 (“Moderate Breeze”; 11–16 knots). During the late autumn and winter, Force 5 (“Fresh Breeze”; 17–21 knots) becomes increasingly frequent, while Force 6 events (“Strong Breeze”; 22–27) occur with regularity, especially after strong cold fronts. Force 7 (“Near Gale”; 28–33 knots) is rather infrequent, while Force 8 events (“Gale”; 34–40 knots) are fairly rare outside of vigorous thunderstorms or squalls. Forces 9–12 generally are associated with tropical storms or hurricanes. In 2005, the Florida Keys experienced all 13 forces on the Beaufort Scale! To download your own copy of the Beaufort Scale, simply point your browser to the following link: http://www.srh.noaa.gov/media/key/Marine/beaufortscale.pdf Remember to be weather-ready, and stay safe!