First Steps: Feel, Observe and Test
The most fundamental way to understand the wind is to use it as a dictionary, where you observe a phenomenon and learn to translate what it means. To start, feel the wind on your body. Turn your face slowly until you feel the breeze equally on both ears; that's the direction the wind is coming from. Ask yourself: is it a light, constant touch or does it come in strong gusts?
Next, observe the environment as a whole. Is the tall grass a few meters away just trembling or constantly leaning? Are the leaves on the bushes still or swaying? The logic is simple: by combining these observations, you begin to have an initial estimate, drastically reducing uncertainty and knowing whether the wind is weak or strong.
A classic and very effective trick to confirm direction is the dust and particles method. Simply grab a handful of fine dust, sand, or dry leaves and release them into the air, at chest height. The path this material takes is the exact route of the wind at that point, showing unequivocally its direction and sense. It's an instant and natural compass.
Environmental Observation Method by Intensity
0 to 2 km/h (approx. 0 to 1 mph): Calm. In this condition, the environment is essentially still. Tree leaves, thin branches, and grass remain motionless. Any dust raised falls vertically and flags or wind socks hang lifelessly against the mast. No wind is felt on the face and silence prevails.
3 to 5 km/h (approx. 2 to 3 mph): Light Air. Here the first signs of movement appear. The most sensitive leaves of trees tremble occasionally and taller ground vegetation shows a slight oscillation. A flag will move enough to indicate wind direction, but without force to fill with air. On the face, the sensation is of an almost imperceptible breeze.
6 to 8 km/h (approx. 4 to 5 mph): Light Breeze. Movement becomes constant. Tree leaves "breathe" and grass leans in a continuous and visible way. Flags begin to rise from the mast and partially fill with air. The wind is felt lightly, but defined and constant, on the face.
9 to 12 km/h (approx. 6 to 7 mph): Gentle Breeze. In this range, thin branches on trees sway rhythmically and the rustling of leaves becomes audible. On the ground, papers, dry leaves, and other light debris are dragged. Flags already extend, although still with visible undulations, and the wind produces a soft whisper as it passes by the ears.
13 to 19 km/h (approx. 8 to 12 mph): Moderate Breeze. The wind force is clear and unmistakable. Shrubs and small trees sway entirely, while dust and loose particles are lifted from the ground. Flags become almost fully extended, with the tip shaking vigorously. A light and constant pressure is felt on the face, which may make the eyes water.
20 to 28 km/h (approx. 13 to 17 mph): Fresh Breeze. The wind now moves larger objects. Tree branches the size of an arm move and the top of trees sways evidently. Flags become fully extended and rigid, possibly snapping with gusts. A clear whistle of wind is heard in the ears and its pressure against the body is felt.
29 to 38 km/h (approx. 18 to 24 mph): Strong Breeze. The environment is dominated by the wind effect. Entire trees sway vigorously and thin branches may be broken. Flags snap loudly and continuously, staying horizontal. The sound of wind passing through structures is clear and it becomes difficult to walk against it.
39 to 49 km/h (approx. 25 to 31 mph): Near Gale. Large tree branches move pronouncedly and a whistle is heard in electrical or telecommunications wires. Using an umbrella becomes difficult and the sensation of wind against the body is of strong resistance.
50 to 61 km/h (approx. 32 to 38 mph): Gale. Entire trees sway with force, including trunks. The inconvenience of walking against the wind is great, requiring effort to maintain balance. Activities such as precision shooting become practically unfeasible.
Flag Method
After having a general idea of wind strength by observing the environment, you may want a more precise number. The flag method is the perfect tool for this. It transforms a visual observation into a concrete numerical data, being ideal when you need more accuracy, such as in shooting activities, drone photography, or aeromodeling.
The logic behind this method is a simple force dispute: the wind force pushing the flag sideways against the force of gravity pulling it down. A stronger wind manages to lift the flag to a greater angle. This consistent relationship between angle and wind force is what allows us to estimate its speed with surprising precision.
The first step is the practice of observation. Visualize the mast as the center of a clock, where the downward position is 0° and the complete horizontal is 90°. Estimate the angle at which the flag is flying. For example, if it's halfway to horizontal, that's 45°. If it's just slightly raised, maybe 30°. If it's almost straight, estimate 80°.
With the estimated angle, the calculation is straightforward. First, divide the angle number by 4. Using our example of 45°, the calculation would be 45 / 4 = 11.25. This result gives you the wind speed in miles per hour (mph). Since in Brazil we use kilometers per hour, the final step is to convert: multiply the result by 1.6. Thus, 11.25 mph * 1.6 = 18 km/h.
The power of this method lies in its ability to refine your reading. You stop having a range, like "between 13 and 19 km/h", and start having a specific number, like "18 km/h". This allows much finer adjustments and a deeper understanding of wind behavior, especially if you compare the reading of a nearby flag with another more distant one.
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