Page 359 - PPL-engelsk 2025

Meteorology

The numbers in the automatically generated METAR may well come from

automatic meters but are checked before publication.

When it says "auto", we must take this into account when we read the METAR

and we must know where errors may be indicated:

- Anemometers are usually stable, so these are probably the same as if an

observer had been sitting there.

- Visibility meters are in automatic visibility meters tubes, where the

translucency in the air is measured. The fact that visibility can be different

in different directions is not taken into account. Therefore, NDV is written,

which indicates that it is a Non Directional Visibility.
- Cloud meters, which measure both the height of clouds and the amount

of clouds, work by sending rays vertically up, and then measuring the

reflection from clouds.

Now, it is not certain that the clouds intend to pass directly over these

meters.

There may be cloud streets (stripes of clouds), and the gaps between the

clouds may pass over the cloud gauge - and then no clouds are observed.

Therefore, slashes /// are indicated, indicating that we should be aware

that there may be clouds close to the aerodrome that are not registered.

3.11.5.5 TREND (Trend Forecast)

A TREND is a brief weather forecast report given at the end of a METAR report,

starting after QNH and ending with =

Example:

Here (at the end): TEMPO 3000 BKN005=

A TREND contains information about any changes in wind, visibility, clouds and

other significant weather factors that may affect the flight.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 359