||Specifications for use at sea
||Specifications for use on land
||Sea like a mirror.
|Calm. Smoke rises vertically.
||Ripples with the appearance of scales are formed, but without foam crests.
|Wind motion visible in smoke.
||Small wavelets, still short, but more pronounced. Crests have a glassy appearance and do not break.
|Wind felt on exposed skin. Leaves rustle.
||Large wavelets. Crests begin to break. Foam of glassy appearance. Perhaps scattered white horses.
|Leaves and smaller twigs in constant motion.
||Small waves, becoming larger; fairly frequent white horses.
|Dust and loose paper is raised. Small branches begin to move.
||Moderate waves, taking a more pronounced long form; many white horses are formed.
|Smaller trees sway.
||Large waves begin to form; the white foam crests are more extensive everywhere.
|Large branches in motion. Whistling heard in overhead wires. Umbrellas use becomes difficult.
||Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind.
|Whole trees in motion. Effort needed to walk against the wind.
||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.
|Twigs broken from trees. Cars veer on road.
||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
|Light structure damage.
||Very high waves with long overhanging 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.
|Trees uprooted. Considerable structural damage.
||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.
|Widespread structural damage.
||The air is filled with foam and spray. Sea completely white with driving spray; visibility very seriously affected.
|Considerable and widespread damage to structures.