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Beaufort Scale

  • One of the first scales to estimate wind speeds and the effects was created by Britain's Admiral Sir Francis Beaufort (1774-1857). He developed the scale in 1805 to help sailors estimate the winds via visual observations. The scale starts with 0 and goes to a force of 12. The Beaufort scale is still used today to estimate wind strengths.


    FORCE
    SPEED MPH
    SPEED KNOTS
    DESCRIPTION
    SPECIFICATIONS FOR USE ON LAND
    IMAGE
    AT IBRSC
    FORCE
    FORCE
    0
    MPH
    MPH
    0-1
    KNOTS
    KNOTS
    0-1
    Calm
    Calm; smoke rises vertically.
    Beaufort Scale Force 0
    Sailors stand around drinking tea.
    FORCE
    1
    MPH
    1-3
    KNOTS
    1-3
    Light Air
    Direction of wind shown by smoke drift, but not by wind vanes.
    Beaufort Scale Force 1
    Very light and patchy: a Solo wins the race!
    FORCE
    2
    MPH
    4-7
    KNOTS
    4-6
    Light Breeze
    Wind felt on face; leaves rustle; ordinary vanes moved by wind.
    Beaufort Scale Force 2
    A nice gentle racing wind. 
    FORCE
    3
    MPH
    8-12
    KNOTS
    7-10
    Gentle Breeze
    Leaves and small twigs in constant motion; wind extends light flag.
    Beaufort Scale Force 3
     A decent racing breeze: things are getting lively.
    FORCE
    4
    MPH
    13-18
    KNOTS
    11-16
    Moderate Breeze
    Raises dust and loose paper; small branches are moved.
     Beaufort Scale Force 4
    Very lively, some capsizes. 
    FORCE
    5
    MPH
    19-24
    KNOTS
    17-21
    Fresh Breeze
    Small trees in leaf begin to sway; crested wavelets form on inland waters.
     Beaufort Scale Force 5
    Probably too much wind for novices unless using reefed Toppers. Much capsizing. 
    FORCE
    6
    MPH
     25-31
    KNOTS
    22-27
    Strong Breeze
    Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty.
     beaufort scale force 6
     Many sailors stay ashore and watch the fun
    FORCE
    7
    MPH
     32-38
    KNOTS
    28-33 
    Near Gale
    Whole trees in motion; direction of wind shown by smoke drift, but not by wind vanes.
     beaufort scale force 7
    Only a few Lasers go out sailing 
    FORCE
    8
    MPH
     39-46
    KNOTS
    34-40
    Gale
    Breaks twigs off trees; generally impedes progress.
     beaufort scale force 8
    Only for the very experienced and foolhardy, and they soon regret it.
    FORCE
    9
    MPH
     47-54
    KNOTS
    41-47
    Severe Gale
    Slight structural damage occurs (chimney-pots and slates removed).
     beaufort scaleforce 9
    Sailors go and check that their boats and those next to them are well tied down. 
    FORCE
    10
    MPH
     55-63
    KNOTS
    48-55
    Storm
    Seldom experienced inland; trees uprooted; considerable structural damage occurs.
     beaufort scale force 10
    Sailors stay at home 
    FORCE
    11
    MPH
     64-72
    KNOTS
    56-63
    Violent Storm
    Very rarely experienced; accompanied by wide-spread damage.
     beaufort scale force 11
    Club Committee organise emergency meeting to discuss new clubhouse roof. Boats blown over fences, rescue boats blown ashore.
    FORCE
    12
    MPH
     73-83
    KNOTS
    64-71
    Hurricane

     beaufort scale force 12
     Michael Fish was right: fortunately we don't get these in the UK.

    Images courtesy of Howtoons


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