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Wind Speed

When measuring the wind speed with an anemometer you discover that the wind is constantly changing speed. It makes more sense to refer to the wind speed as a range of speeds. For example you would say that the wind speed was between 4 miles per hour and 8 miles per hour.

This is the beauty of the Beaufort scale it groups wind speeds into logical groups and assigns a single number to that group of wind speeds. This makes it easier to refer to the speed using a single number. This number can then be understood by anyone whether they are more familiar with mph or kph. I suggest that you become familiar with using the Beaufort scale.

The National Weather Service has an interesting article about the Beaufort scale. It includes a history and pictures that show what the sea looks like at each Beaufort number.

I would caution you not to make numerical estimates of wind speeds if you have not used an anemometer to verify your estimations. It is ok if the estimates are for your personal use, but be careful to qualify your observations when sharing them with someone else.

Before I had a wind measuring device my estimates were as much as 6 mph too high. This would translate to a Beaufort number higher by 2. Learn to read the wind signs for Beaufort 1, 2, and 3. Kite selection in these three ranges is more critical. In Winds of 4 Bft. and above just about anything will fly.



0 Beaufort (Bft)- Too light for flying any type of KAP equipment unless you are using the "No-Wind" techniques.

1 Bft.- Still too light for most KAP applications. You might be able to use a Dopero to lift a rig that weighed 0.5# (227g). That would be a disposable camera with an ice trigger and a balsa cradle.

2 Bft.- The upper half of 2 Bft. is where serious KAP work can begin although you need the right kite and light cradles. My LASS rig with a Dopero works great in this range.

3 Bft.- You can lift most cradles with most kites.

4 Bft.- Winds generally dictate going to smaller kites to cut down on the amount of pull.

Bft. 5 and above- I don't fly. That is my personal preference. At these wind speeds the experience ceases to be fun.

Bft. 6-7- I have lost a kite and cradle in winds that were between 6 and 7 Bft. when my 200# line broke.

 

USING FLAGS TO ESTIMATE THE WIND SPEED

0 Bft- I assume you can guess what this looks like.

1 Bft- the flag only occasionally flips open, the outer end hangs lower.

2 Bft- the flag is mostly extended, the waves are deep, a large portion of the outer top corner flips back and forth.

3 Bft- the flag is completely extended, the waves are faster and smaller than 2 Bft.

4 Bft and Up- the flag is still completely extended, the waves are faster than 3 Bft. The changes from 4 Bft. and up are more subtile and harder to distinguish from each other, but this is of little concern since the choice is not what kite to fly, but whether to fly a kite at all.

These flags are 5 ft. by 7 ft. (1.5m by 2m) but size makes little difference.

(If you are using Internet Explorer and have javascript disabled then the flag animations are about 3/4 normal speed. Netscape plays the animations at normal speed with or without javascript enabled.)

 

WIND SPEED SCALE

Wind Speed at 10m Height

mph kph m/s Beaufort Description*
0-1 0-2 0-0.6 0 Calm
1-3 2-6 0.6-1.7 1 Light air
4-7 7-11 1.9-3.1 2 Light breeze
8-11 12-19 3.3-5.3 3 Gentle breeze
12-18 20-30 5.6-8.3 4 Moderate breeze
19-24 31-39 8.6-10.8 5 Fresh breeze
25-31 40-50 11.1-13.9 6 Strong breeze
31-38 50-61 13.9-16.9 7 Near gale
38-47 61-74 16.9-20.5 8 Gale
47-56 75-87 20.8-24.2 9 Strong gale
56-65 88-101 24.4-28.1 10 Storm
65-76 102-117 28.3-32.5 11 Violent storm
>76 >118 >32.7 12 Hurricane