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Secrets of the St. Lawrence

Extra - Beaufort

Extra (PDF; 62 KB)

ForceWind SpeedDescriptive TermEffects Observed at SeaEffects Observed on Land
0Less than 1Less than 1CalmSea surface like a mirror, but not necessarily flat.Smoke rises vertically.
11 - 51 - 3Light airRipples with the appearance of scales are formed, but without foam crests.Direction of wind shown by smoke drift, but not wind vanes.
26 - 114 - 6Light breezeSmall wavelets, still short but more pronounced. Crests do not break. When visibility good, horizon line always very clear.Wind felt on face. Leaves rustle. Ordinary vane moved by wind.
312 - 197 - 10Gentle breezeLarge wavelets. Crests begin to break. Foam of glassy appearance. Perhaps scattered whitecaps.Leaves and small twigs in constant motion. Wind extends light flag.
420 - 2811 - 16Moderate breezeSmall waves, becoming longer. Fairly frequent whitecaps.Raises dust and loose paper. Small branches are moved.
529 - 3817 - 21Fresh breezeModerate waves, taking a more pronounced long form. Many whitecaps are formed. Chance of some spray.Small trees with leaves begin to sway. Crested wavelets form on inland waters.
639 - 4922 - 27Strong breezeLarge waves begin to form. The white foam crests are more extensive everywhere. Probably some spray.Large branches in motion. Whisteling heard in telephone wires. Umbrellas used with difficulty.
750 - 6128 - 33Near galeSea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind.Whole trees in motion. Inconvenience felt in walking against wind.
862 - 7434 - 40GaleModerately high waves of greater length. Edges of crests begin to break into the spindrift. The foam is blown in well-marked streaks along the direction of the wind.Breaks twigs off trees. Generally impedes progress. Walking into wind almost impossible.
975 - 8841 - 47Strong galeHigh 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.Slight structural damage occurs, e.g. roofing shingles may become loose or blow off.
1089 - 10248 - 55StormVery high waves with long overhanging crests. Dense white streaks of foam. Surface of the sea takes a white appearance. The tumbling of the sea becomes heavy and shock-like. Visibility affected.Trees uprooted. Considerable structural damage occurs.
11103 - 11756 - 63Violent stormExceptionally high waves. Sea completely covered with long white patches of foam. Visibility affected.Widespread damage.
12118 - 13364 - 71HurricaneAir filled with foam and spray. Sea entirely white with foam. Visibility seriously impaired.Rare.
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