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# Wind Speed Direction and Strength

We can describe the wind by talking about its strength or speed and the direction in which it is blowing. This lesson explains about how to monitor wind Speed Direction and Strength and the weather instruments to measure wind Speed Direction and Strength.

## How to monitor wind speed direction and strength

Examples of weather instruments

• Wind sock – To monitor wind direction
• Anemometer – To monitor wind speed
• The Beaufort scale – To monitor wind strength

## How can we tell which way the wind is blowing?

• By looking at a weather vane on a tower or church
• By the compass

E.g. – * North wind blows from the North towards the South.

* South wind blows from the South towards the North.

## The Wind Sock

### What is the wind sock?

The wind sock is a long cloth tube through which the wind is funneled.

### What does the wind sock show us?

It shows both the direction and strength of the wind.

E.g. – The straighter the sock, the stronger the wind.

• At airports
• At airfields
• At ports

## Prevailing winds

### What are prevailing winds?

The winds that almost always blow from the same direction are called prevailing winds.

### What is the most frequent prevailing wind in Britain?

The westerlies or westerly winds are the most frequent prevailing winds in Britain.

### What is the behaviour of this wind?

These move across the Atlantic Ocean bringing windy, wet weather to the high mountains and moorlands in the west. Land east of these areas is drier.

## Anemometer

### What is an Anemometer?

An Anemometer is the scientific instrument for measuring wind speed. It comes with four little cups attached by a shaft, to a meter or to a scale. The four little cups turn in the wind. When the wind blows harder, the cups of the anemometer turn faster and that is the higher reading on the meter.

## The Beaufort scale

We can estimate the speed of the wind by seeing what effect it has on smoke, flags and tree branches.

### What is the Beaufort scale?

This is a scale used to measure the strength of the wind. The Beaufort scale is a system of recording wind strength invented in 1805 by Sir Francis Beaufort. It is a numerical scale ranging from 0 for calm to 12 for a hurricane. Sailors and forecasters use the Beaufort Wind Scale as a standardized way to rate wind strength.

 Beaufort Scale Windkm/hr Effects on land 0 Below 1 Smoke rises straight up; tree leaves without perceptible motion 1 1 – 6 Rising smoke drifts; tree leaves barely move 2 7 – 12 Leaves rustle slightly; wind felt on face 3 13 – 19 Leaves and twigs move; loose paper and dust raised from ground 4 20 – 30 Small branches move; wind raises dust and paper 5 31 – 39 Small trees sway and large branches in motion; dust clouds raised 6 40 – 50 Large branches move continuously; wind whistles; umbrellas difficult to use 7 51 – 62 Whole trees in motion; walking difficult 8 63 – 74 Tree twigs break; walking progress slow 9 75 – 87 Slight structural damage 10 88 – 102 Exposed trees uprooted; heavy structural damage 11 103 –  117 Widespread damage 12 Above 118 Severe damage and destruction

Also, read the lesson Wind Facts Wind Formation Wind Classification.