Wind

Surface Wind

Surface wind speed is measured by an anemometer, while wind direction is measured by a wind vane.

For aviation weather observations, the surface wind is measured at a standard height of approximately 10 metres above the ground to reduce the effects of local surface disturbances.

Wind Speed

Wind speed in New Zealand aviation is given in knots (kt).

Wind Direction

Wind direction describes the direction from which the wind is blowing.

Directions are measured clockwise from north through 360°.

For example:

270°/15 kt means a wind:

• from 270°;

• at 15 knots.

True and Magnetic Wind Direction

Wind direction in aviation weather forecasts and observations such as:

• TAF;

• METAR; and

• AAW

is given in degrees True.

Surface winds provided to pilots by ATC or ATIS are given in degrees Magnetic.

Forces Affecting the Wind

The three main forces affecting low-level wind are:

• Pressure Gradient Force

• Coriolis Force

• Friction

Pressure Gradient Force

Air naturally tends to move from an area of high pressure towards an area of low pressure.

The force causing this movement is called the Pressure Gradient Force.

It acts: