• Beaufort scale
    The Beaufort scale describes the force of winds.

    Photograph by Otis Imboden

    Hurricane Warning
    Hurricane warnings are issued when winds reach 12 on the Beaufort scale. But actual hurricane categories are determined by different factors. A 12 on the Beaufort scale is a Category 1 (lowest level) hurricane, but a 13 on the Beaufort scale is not Category 2it's actually much, much stronger.

    The Beaufort scale, officially known as the Beaufort wind force scale, is a descriptive table. It depicts the force of wind by a series of numbers from 0 to 12. Actually, the Beaufort scale goes all the way to 17, but the last five numbers only apply to tropical typhoons. These numbers are only used in the areas around China and Taiwan.

    The scale is named for Sir Francis Beaufort of the British Royal Navy. In 1805, he devised a method of describing wind force according to procedures for setting sails on a warship.

    The Beaufort scale is useful for estimating wind power without wind instruments.

    0: Calm and still.

    Smoke rises vertically.

    1. Light winds at 1-5 kph (1-3 mph).

    Smoke drift shows wind direction.

    2. Light breeze at 6-11 kph (4-7 mph).

    Wind can be felt on face, flag ripples.

    3. Gentle breeze at 12-19 kph (8-12 mph).

    Flag waves.

    4. Gentle breeze at 20-28 kph (13-18 mph).

    Paper and leaves are scattered.

    5. Fresh breeze at 29-38 kph (19-24 mph).

    Small trees sway, whitecaps form on waves.

    6. Strong breeze at 39-49 kph (25-31 mph).

    Umbrellas are hard to use, large branches on trees move.

    7. Moderate gale at 50-61 kph (32-38 mph).

    Trees sway, walking in the wind is difficult.

    8. Fresh gale at 62-74 kph (39-46 mph).

    Twigs and branches break off of trees.

    9. Strong gale at 75-88 kph (47-54 mph).

    Roof tiles blow off buildings.

    10. Whole gale at 89-102 kph (55-63 mph).

    Trees are uprooted.

    11. Storm at 103-118 kph (64-73 mph).

    Widespread damage to vegetation and buildings, nearly no visibility at sea.

    12. Hurricane at 119-220 kph (74-136 mph).

    Category 1 hurricane, Category 1 tornado. Widespread destruction.

  • Term Part of Speech Definition Encyclopedic Entry
    Beaufort scale Noun

    scale measuring wind forces, generally from 0 to 12.

    Encyclopedic Entry: Beaufort scale
    breeze Noun

    light wind or air current.

    depict Verb

    to illustrate or show.

    estimate Verb

    to guess based on knowledge of the situation or object.

    gale Noun

    strong wind or air current.

    hurricane Noun

    tropical storm with wind speeds of at least 119 kilometers (74 miles) per hour. Hurricanes are the same thing as typhoons, but usually located in the Atlantic Ocean region.

    indicate Verb

    to display or show.

    procedure Noun

    method or steps followed to achieve a goal.

    ripple Verb

    to form very small waves.

    Royal Navy Noun

    armed service branch of the United Kingdom.

    Sir Francis Beaufort Noun

    (17741857) British hydrographer and Navy officer.

    storm Noun

    severe weather indicating a disturbed state of the atmosphere resulting from uplifted air.

    tornado Noun

    a violently rotating column of air that forms at the bottom of a cloud and touches the ground.

    tropical Adjective

    existing in the tropics, the latitudes between the Tropic of Cancer in the north and the Tropic of Capricorn in the south.

    typhoon Noun

    tropical storm with wind speeds of at least 74 miles (119 kilometers) per hour. Typhoons are the same thing as hurricanes, but usually located in the Pacific or Indian Ocean region.

    uproot Verb

    to tear or remove a tree or other plant by the roots.

    vegetation Noun

    all the plant life of a specific place.

    warship Noun

    seagoing vessel built for armed conflict.

    wind Noun

    movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.

    wind instrument Noun

    tool or device used to measure the strength, direction, or other characteristic of wind.

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