Flight Simulator: Decoding a METAR weather report


Flight Simulator: Decoding a METAR weather report

METAR is a weather observation report commonly used in aviation. Their emitting source is an airfield. The purpose of this international code is to help and simplify the reading of meteorological information. Basic data is common to all countries, but some sections of the code are subject to local variations. In Microsoft Flight Simulator, you notice that the METARs are used in order to give in a few terms complete information on the weather.

You can get this information through several tools. First of all, on the Internet via a large number of sites; we offer this site as an example. ATIS can also give the METAR of the field (every hour against 30 mins for a METAR). In Microsoft Flight Simulator, you can connect to it through the radio menu. Please note, the ATIS will provide other information than the METAR such as a NOTAM (information on a closed runway etc.) 

First of all, let's differentiate METAR and TAF, although they are often associated:

METAR : aerodrome weather observation report: this is the current weather detected by the weather station of the aerodrome in question.

TAF : aerodrome weather forecast report: this is the forecast from the weather station of the aerodrome in question. There are 2 types of TAFs, "short" TAFs valid until 9am, and "long" TAFs valid from 24 hours to 30 hours.


As we explained above, METARs are attached to their own transmitting station, in this case an aerodrome. It is therefore logical that the message begins with the name of the aerodrome in question, in the form of an ICAO code consisting of 4 letters. The ICAO code is made up of 4 letters allowing the terrain to be identified, for example, for Orly airport, the METAR will start with "LFPO".

Just after the field code, we will find there the date and time of production of the message (in Zulu time, that is to say world time GMT / UTC. For us in France, we simply have to subtract 1 hour from the winter and 2h summer So here is the formatting of this information: 161830Z, the 16th means METAR day, and 1830… 6.30pm Zulu.

In many cases, you will see the term AUTO below , meaning that the message was created automatically and autonomously by the weather station and not by a human presence. Be careful, this sometimes results in certain parameters that are slightly distorted in reality. Indeed, if there is a very small disruptive air mass around the station and a blue sky storm over the entire region, the message can sometimes hold some surprises.

Then comes this type of information: 14015KT. These are winds , expressed in knots. This is translated in this example by a wind coming from 140 ° for an average force of 15 knots over 10 minutes . You can sometimes find additional information there, for example if there are gusts of wind (greater than 10 knots than the average wind), we will see: GXXKT, “G” meaning “gust” and ” XX ”the value of the bursts. The wind can sometimes be from an imprecise source (when it is very weak, less than 3 knots), in this case it will be for example VRB02KT. We know that it is blowing for 2 knots, from an unknown direction! But for 2 knots, that shouldn't be too much of a problem ... On the contrary, when it is more important, but in a variable direction, we will read in addition to the average wind 240V350 (this is an example), the wind will therefore be variable between 240 ° and 350 °.

Regarding the knowledge of the runway in service via the METAR, it should be noted that this information is normally indicated by the human presence in the control tower.

If the aerodrome is in auto-info, it will be up to you to determine it. A plane takes off and lands always headwind . And remember the wind shown in the METAR indicates where it is coming from. Example, if the Metar indicates: Wind 27014G25KT and you are on the Périgueux field with a track 29 and 11, which one do you take?

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