How to Measure the Wind

 


If you can't see the wind, how can you tell how fast it is moving?

Actually, it's very easy. You can't see the wind, but you can see what it does to other things around you. You know it is windy because you can feel the breeze on your face. You can see the leaves in the trees outside shaking. You hear the flag at the post office down the street waving very proudly.

On days when the flag waves, the wind is moving faster than you can ride your bicycle, even when you pedaled very hard.

Let's talk about wind speed. We will describe it in miles-per-hour. That's the same way we describe how fast a car moves. But instead of looking at the car's speedometer, we will use the natural wind speedometer that is all around us in nature.

Natural Wind Speedometer

    
1-3
mph
     
Smoke drifts lazily, branches are still, flags hang limp
    
4-7
mph
     
Tree leaves rustle, flags move slowly
    
8-12
mph
     
Flags fly, bushes shake, leaves move
    
13-18
mph
     
Small branches shake, grass moves
    
19-24
mph
     
Large branches sway, flags flap noisily
    
25-31
mph
     
Trees shake, dust and sand flies

The best time to fly a kite is when the wind is between 4 and 12 miles-per-hour. If the wind is less, then most kites have problems flying. If the wind is more, then most kites will lose control. So watch the trees, bushes, flags and grass to know when the wind is just right.

The other thing to watch for is wind turbulence. Turbulence is what happens when the wind gets bumpy. And it is very difficuklt to fly a kite well in bumby wind.

Turbulence Turbulence

Think of wind flowing over the land just like water flows down a river. If the river is wide and smooth, the water will bne smooth too. But if the river is going over rocks, around curves, or downhill, it will run fast and rough.

The same thing happens to wind when it flows over trees, past buildings, or over hills.

Turbulence

Kite fliers have a rule. We know that wind will be bumpy after going over or around an obstacle. We have measured how long it takes to smooth out. That distance is seven times the hight of the obstacle. So if a tree is 100 feet tall, you need to be 700 feet away from the tree to avoid the bumpy wind. Otherwise, the wind may reach out and pull your kite into the tree or crash it to the ground.

Wind Speed
Performance and Comparison

mph kph knots bft wind type visible signs kite flying

0

0

0

0

still

no movement,
smoke rises
vertically in a column

tell stories
drink beer

1-3

1-7

1-3

1

light air

smoke drifts
branches & grass
move slightly

minimal performance
ultralight kites

4-7

8-11

4-6

2

slight breeze

leaves move slightly
flags flap solwly

moderate flying
some lifters & laundry

8-12

12-20

7-11

3

gentle breeze

flags flap slowly
wind felt on face

ideal flying
fully laundry
on all kites

13-18

21-28

12-16

4

moderate breeze

small branches
move, dust blows

check anchors
heavier flying line

19-24

29-38

17-21

5

fresh breeze

small trees sway
wavelets on water

stops being fun
exercise caution

25-30

39-50

22-28

6

wind

large branches
move, sand blows
trees in motion

extreme conditions
get help and land kites

31-40

51-65

29-35

7

strong wind

whole trees in motion

tell stories
drink beer

*

Material courtesey of David Gomberg.
Copyright © 2008 Gomberg Kite Productions International Inc. All rights reserved.