How to describe wind strength

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29.09.2013 Posted in Wind & weather No Comments
What is the wind strenght?

When preparing to go windsurfing it is essential to know what the wind strength is, as well as to describe it to others. This helps you choose the appropriate equipment and also prepare mentally as to what conditions you will meet on the water, and communicating conditions helps your mates do the same. As you might know there are several units that can be used to describe the strength of the wind. But which out of them should you use?

Which unit to use to describe wind strength?

There are several units that can be used to describe the strength of the wind. Windguru for instance allows their visitors to choose between the following units when displaying their wind forecasts:

Which one out of these you choose is not significant in it self, the important thing is that you understand the unit you have chosen well enough to adjust choice of equipment and behaviour on the water accordingly.

Myself I prefer to use the Beaufort wind force scale. The reason is simple – it is due to personal preference and practicality:

  • My forecast sources use the Beaufort scale
  • I have over the years learnt how to quite accurately tell the current wind force by looking at and sensing my surroundings
  • I have established easy to follow rules as to what equipment to choose for each level of the scale
  • It is easy to communicate to, and understand for the other guys I go windsurfing together with
  • I find it somewhat simpler to understand and use than the alternatives due to a limited number of levels with easy to remember descriptors

If all your windsurfing mates are using another unit, or forecasts are available in one specific unit, there is no reason for you to chose another unit than that as your basic scale. Anything else would be a source of confusion and misunderstanding.

Using the Beaufort scale

If you still are not sure as to unit choice, my advice would be to go with the Beaufort scale. Although it is not considered modern, I find it’s number of levels manageable and it’s levels’ physical descriptions quite easy to remember.

The  Beaufort scale was originally developed in order to describe wind strength and the effect it had on the sails of a frigate. It was divided into 13 forces and used in a qualitative manner to describe the wind strength. From “just sufficient to give steerage” to “that which no canvas sails could withstand”. Modern versions of the scale have a mathematical relationship with the metric system, and also include levels 13 to 17, but trust me – the latter are conditions you would never dream of windsurfing in (unless you are a part of Red Bull’s Storm Chase)!

The following table has been borrowed from this Wikipedia article. The best way to get accustomed to it is actively to start determining the wind strength whenever you are outside. Use all your senses and try to recognise both the land and sea signs described in the table. After some practice you will notice that you automatically will have classified the current wind’s direction and force, even without having thought about it first!

Force Wind speed Description Sea conditions Land conditions
0 < 0.3 m/s Calm Flat. Calm. Smoke rises vertically.
1 0.3–1.5 m/s Light air Ripples without crests. Smoke drift indicates wind direction. Leaves and wind vanes are stationary.
2 1.6–3.4 m/s Light breeze Small wavelets. Crests of glassy appearance, not breaking. Wind felt on exposed skin. Leaves rustle. Wind vanes begin to move
3 3.5–5.4 m/s Gentle breeze Large wavelets. Crests begin to break; scattered whitecaps. Leaves and small twigs constantly moving, light flags extended.
4 5.5–7.9 m/s Moderate breeze Small waves with breaking crests. Fairly frequent whitecaps. Dust and loose paper raised. Small branches begin to move.
5 8.0–10.7 m/s Fresh breeze Moderate waves of some length. Many whitecaps. Small amounts of spray. Branches of a moderate size move. Small trees in leaf begin to sway.
6 10.8–13.8 m/s Strong breeze Long waves begin to form. White foam crests are very frequent. Some airborne spray is present. Large branches in motion. Whistling heard in overhead wires. Umbrella use becomes difficult. Empty plastic bins tip over.
7 13.9–17.1 m/s High wind, moderate gale, near gale Sea heaps up. Some foam from breaking waves is blown into streaks along wind direction. Moderate amounts of airborne spray. Whole trees in motion. Effort needed to walk against the wind.
8 17.2–20.7 m/s Gale, fresh gale Moderately high waves with breaking crests forming spindrift. Well-marked streaks of foam are blown along wind direction. Considerable airborne spray. Some twigs broken from trees. Cars veer on road. Progress on foot is seriously impeded.
9 20.8–24.4 m/s Strong gale High waves whose crests sometimes roll over. Dense foam is blown along wind direction. Large amounts of airborne spray may begin to reduce visibility. Some branches break off trees, and some small trees blow over. Construction/temporary signs and barricades blow over.
10 24.5–28.4 m/s Storm, whole gale Very high waves with overhanging crests. 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, structural damage likely.
11 28.5–32.6 m/s Violent storm 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 and structural damage likely.
12 ≥ 32.7 m/s Hurricane Huge waves. Sea is completely white with foam and spray. Air is filled with driving spray, greatly reducing visibility. Severe widespread damage to vegetation and structures. Debris and unsecured objects are hurled about.

Source: Wikipedia

/Alex

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