THE BEAUFORT WIND 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.

	The Beaufort scale
	For use at sea
	For use on land

FORCE  EQUIVALENT SPEED   DESCRIPTION      SPECIFICATIONS FOR USE AT SEA
     10 m above ground
     miles/hour  knots
1       1-3      1-3      Light air        Ripples with the appearance of scales are formed,
                                           but without foam crests.

2       4-7      4-6      Light Breeze     Small wavelets, still short, but more pronounced.
                                           Crests have a glassy appearance and do not break.

3       8-12     7-10     Gentle Breeze    Large wavelets. Crests begin to break. Foam of 
                                           glassy appearance. Perhaps scattered white horses.

4      13-18    11-16     Moderate Breeze  Small waves, becoming larger; fairly frequent white 
                                           horses.

5      19-24    17-21     Fresh Breeze     Moderate waves, taking a more pronounced long form; 
                                           many white horses are formed. Chance of some spray.

6      25-31    22-27     Strong Breeze    Large waves begin to form; the white foam crests are
                                           more extensive everywhere. Probably some spray.

7      32-38    28-33     Near Gale        Sea heaps up and white foam from breaking waves 
                                           begins to be blown in streaks along the direction
                                           of the wind.

8      39-46    34-40     Gale             Moderately high waves of greater length; edges of 
                                           crests begin to break into spindrift. The foam is
                                           blown in well-marked streaks along the direction
                                           of the wind.

9      47-54    41-47     Severe Gale      High waves. Dense streaks of foam along the direction
                                           of the wind. Crests of waves begin to topple, tumble
                                           and roll over. Spray may affect visibility.

10     55-63    48-55     Storm            Very high waves with long over-hanging crests.
                                           The resulting foam, in great patches, is blown                                           
                                           in dense white streaks along the direction of the
                                           wind. On the whole the surface of the sea takes on
                                           a white appearance. The 'tumbling' of the sea 
                                           becomes heavy and shock-like. Visibility affected.

11    64-72     56-63     Violent Storm    Exceptionally high waves (small and medium-size ships
                                           might be for a time lost to view behind the waves).
                                           The sea is completely covered with long white patches
                                           of foam lying along the direction of the wind. 
                                           Everywhere the edges of the wave crests are blown 
                                           into froth. Visibility affected.

12    73-83     64-71     Hurricane        The air is filled with foam and spray. Sea completely
                                           white with driving spray; visibility very seriously
                                           affected.

For use at sea
For use on land
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FORCE  EQUIVALENT SPEED   DESCRIPTION      SPECIFICATIONS FOR USE ON LAND
     10 m above ground
     miles/hour  knots
0       0-1      0-1      Calm             Calm; smoke rises verticall.

1       1-3      1-3      Light air        Direction of wind shown by smoke drift, but not
                                           by wind vanes.
                                          
2       4-7      4-6      Light Breeze     Wind felt on face; leaves rustle; ordinary vanes
                                           moved by wind.

3       8-12     7-10     Gentle Breeze    Leaves and small twigs in constant motion; wind
                                           extends light flag.

4      13-18    11-16     Moderate Breeze  Raises dust and loose paper; small branches are
                                           moved.

5      19-24    17-21     Fresh Breeze     Small trees in leaf begin to sway; crested wavelets
                                           form on inland waters.

6      25-31    22-27     Strong Breeze    Large branches in motion; whistling heard in
                                           telegraph wires; umbrellas used with difficulty.

7      32-38    28-33     Near Gale        Whole trees in motion; inconvenience felt when
                                           walking against the wind.

8      39-46    34-40     Gale             Breaks twigs off trees; generally impedes progress.

9      47-54    41-47     Severe Gale      Slight structural damage occurs (chimney-pots and
                                           slates removed).

10     55-63    48-55     Storm            Seldom experienced inland; trees uprooted;
                                           considerable structural damage occurs.

11    64-72     56-63     Violent Storm    Very rarely experienced; accompanied by wide-spread
                                           damage.

12    73-83     64-71     Hurricane                        --

For use at sea
For use on land
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