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Wind Speed

This refers to the sustained average wind speed, normally averaged over a period of 10 minutes for up to 3 hrs.

The gust shown is usually the highest wind speed at any time in the forecast period averaged over a period of 3 seconds.

The gusts shown here are likely to be the mean values for the area as are the average winds and they do not take account of very localised effects such as funnelling between building and sheltering behind hills and walls or within a forest.

The winds we show in our forecast are what we would expect if you were in a reasonably exposed location. The units can be selected in the drop down menu on this web site.

The following table known as the Beaufort Table is a useful way that we have categorised winds – originally developed for mariners as they used to estimate wind speeds by looking at the waves. The scale is now also adapted for land as shown in the last column.

Beaufort Wind Force scale
Number Wind Speed Description Wave Height Sea Conditions Land Conditions
mph kts m ft
0 1 1 Calm 0 0 Flat Calm. Smoke rises vertically.
1 1-3 1-2 Light air 0.1 0.33 Ripples without crests. Wind motion cisible in smoke.
2 3-7 3-6 Light breeze 0.2 0.66 Small wavelets. Crests of glassy appearance, not breaking Wind felt on exposed skin. Leaves rustle.
3 8-12 7-10 Gentle breeze 0.6 2 Large wavelets. Crests begin to break; scattered whitecaps Leaves and small twigs constant motion.
4 13-17 11-15 Moderate breeze 1 3.3 Small waves. Dust and loose paper raised. Small branches begin to move.
5 18-24 16-20 Fresh breeze 2 6.6 Moderate(1.2m) longer waves.Some foam and spray. Branches of a moderate size move. Small trees begin to sway.
6 25-30 21-26 Strong breeze 3 9.9 Long waves with foam crests and some spray. Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic garbage cans tip over.
7 31-38 27-33 High wind, moderate gale, near gale 4 13.1 Sea heaps up and foam begins to be blown in streaks in wind direction. Whole trees in motion. Effort needed to walk against the wind. Swaying of skyscrapers may be felt, especially by people on upper floors.
8 39-46 34-40 Fresh gale 5.5 18 Moderately high waves with breaking crests forming spindrift. Streaks of foam. Twigs broken from trees. Cars veer on road.
9 47-54 41-47 Strong gale 7 23 High waves(6-7m) with dense foam. Wave crests start to roll over. Considerable spray. Some branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over. Damage to circus tents and canopies.
10 55-63 48=55 Whole gale, storm 9 29.5 Very high waves. Large patches of foam from wave crests give the sea a white appearance. Considerable tumbling of waves with heavy impact. Large amounts of airborne spray reduce visibility. Trees are broken off or uprooted, saplings bent and deformed, poorly attached asphalt shingles and shingles in poor condition peel off roofs.
11 64-72 56-63 Violent storm 11.5 37.7 Exceptionally high waves. Very large patches of foam, driven before the wind, cover much of the sea surface. Very large amounts of airborne spray severely reduce visibility. Widespread vegetation damage. More damage to most roofing surfaces, asphalt tiles that have curled up and/or fractured due to age may break away completely.
12 ≥ 73 ≥ 64 Hurricane force ≥ 14 ≥ 46 Huge waves. Sea is completely white with foam and spray. Air is filled with driving spray, greatly reducing visibility. Considerable and widespread damage to vegetation, a few windows broken, structural damage to mobile homes and poorly constructed sheds and bams. Debris may be hurled about.