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Beaufort Wind Scale

Wind: Gullsweep's® Energy

Besides the traditional cloud evaluation and sun set color, there is a basic scale for mariners to evaluate wind speed. It's known as the Beaufort Wind Scale, created in 1806 by Francis Beaufort. It is a numerical scale ranging from 0 for calm to 12 for a hurricane. Sailors and forecasters use the Beaufort Wind Scale as a standardized way to rate wind speed. The scale, when originally drawn up, categorized wind not by its speed but by its observable effects. Various attempts have been made since to apply precise speeds to the Beaufort ratings.

Beaufort Scale Wind: km/hr Speed:
Effects on Land Effects on Water
0 below 1 below 1 Smoke rises straight up; tree leaves without perceptible motion Sea flat and mirror like
1 1 - 6 1 - 3 Rising smoke drifts; tree leaves barely move Ripples without foam on crests appear
2 7 - 12 4 - 7 Leaves rustle slightly; wind felt on face Small wavelets form, with short but pronounced crests that do not break
3 13 - 19 8 - 12 Leaves and twigs move; loose paper and dust raised from ground Large wavelets with breaking crests form; occasional white foam crests
4 20 - 30 13 -18 Small branches move; wind raises dust and paper Small waves form; white foam at crests more frequent
5 31 - 39 19 - 24 Small trees sway and large branches in motion; dust clouds raised Moderate waves occur, with foaming crests and possible spray
6 40 - 50 25 - 31 Large branches move continuously; wind whistles; umbrellas difficult to use Large waves form, with extensive white foam crests
7 51 - 62 32 - 38 Whole trees in motion; walking difficult Sea heaps; white foam blows in streaks from breaking waves
8 63 - 74 39 - 46 Tree twigs break; walking progress slow Moderately high waves form, well-marked streaks of foam blow with wind
9 75 - 87 47 - 54 Slight structural damage High waves form, with dense streaks of foam
10 88 - 102 55 - 63 Exposed trees uprooted; heavy structural damage Very high waves with long overhanging crests occur; great patches of foam blows in dense white streaks
11 103 - 117  64 - 72 Widespread damage Exceptionally high waves form; sea covered with long white patches of foam; wave crests blown into froth
12 above 118 above 73 Severe damage and destruction Exceptionally high waves form; air filled with foam and spray; sea completely white

Source: National Oceanic and Atmospheric Administration

Gullsweep® Users - Be Aware:
Tests have been made at wind velocities in excess of 60 miles per hour with no adverse effects. However, we recommend that GULLSWEEP® should be removed and stored away when winds are in excess of 35 mph as birds will not be roosting in such a wind, and the high rotation rate will not improve the life of the GULLSWEEP®.