Kristine Laoey, age 9, of Commerce Ga

How does the weatherman know wind speed?

It is no easy job to measure the exact speed of the .wind. Perhaps we can clock it by how fast it blows a tumbleweed or bit of paper, Not that  is no reliable record, The tumbleweed stops and starts. The gusty wind whips a bit of paper up and around the street corners, Maybe we could clock the fastest spurt of a tumbleweed or bit of paper. No for the same wind blows a leaf or a light feather faster and farther. So we cannot pace the wind to get a reliable estimate of its speed.

Men on old sailing ships figured that the strongest wind blows the fastest, Sir Francis Beauforti an English sea captain worked out a wind scale in 1806. Our weatherman often uses an improved Beaufort scale to give us a general idea of the speed of the wind.

When he says the wind is light he means it is blowing less than 7 miles per hour and may be too weak to move the weather vane. A gentle breeze is 8 to 12 miles an hour. It has just enough strength to flap a flag, A moderate wind is between 13 and 18 miles per hour. It raises the dust and lifts bits of paper. Afresh wind of 19 to 24 miles an hour can sway small trees and ruffle the pond. A strong wind of 25 to 38 miles an hour can bend branches and whistle through telegraph wires. A gale wind is 39 to 54 miles an hour and can blow shingles off the roof. A whole gale of 55 to 75 miles an hour can uproot a tree. At 75 miles an hour, the wind reaches hurricane speed and almost anything can happen.

As you see, these estimates of wind speed are gauged by its strength or force. The weatherman gets his information from an instrument more accurate than rustling leaves and tumbling chimney pots, He uses an anemonometer. This word is easy when you remember that the anemone is the vand flower. But even the anemonometer cannot pace the wind. It estimates the speed from the wind’s force, or pressure.

There is a direct relationship between the strength of the wind and its speed. You can feel he winds pressure in you` aces the same pressure that flaps ,the flag and and tumbles the shingles, We can estimate the force of the wind in pressure per square foot. And the pressure of the wind is proportional to the square of its speed, If we know the pressure we can figure out the speed, A 20 miles wind pushes with four times more pressure than a 10 mile wind,

There are several types of anemonometer for checking the strength of the wind and translating it into miles per hour. One has three or four cups or hollow cones on top of a revolving rod; The wind blows them around faster or slower$ depending upon its strength. A clock‑like gadget , translates the pressure into speed. The record is made on a revolting drum in wavy lines of ink. The lines are wavy because of the gustiness of the wind, For this reasons no fair estimate of wind speed can be made in less than one minute: