Meteorological Aerodrome Reports (METARs) — Page 484, Lesson 459

I want to walk you through Meteorological Aerodrome Reports — METARs. This is the start of that topic, so let's build it from the ground up. First, the term itself: METAR stands for Meteorological Aerodrome Report. These are routine weather observations issued at aerodromes, and as a professional pilot you will consult them constantly — for your departure aerodrome, your destination, and for aerodromes along your route, especially those upwind of your destination, so you can see what weather is approaching. Now, not every aerodrome has a human observer on duty. Many aerodromes that are not used on a regular basis, or that have limited staff available, use automatic meteorological stations to generate the METARs. When that happens, the report includes the word "AUTO" in the body. Let me show you an example: EGDL 070650Z AUTO 03013KT //// // FEW110/// 09/06 Q1023 = Let's decode what we see. The first group is the ICAO location indicator — EGDL is Lyneham. Then the date-time group: 070650Z means the 7th day of the month at 0650 Zulu time, which is UTC. Then we see the word "AUTO", telling us this report was generated automatically. Next comes the surface wind: 03013KT means the wind is from 030 degrees at 13 knots. Then we hit something unusual — four slashes: ////. That's the visibility group. Then two more slashes: //. That's the present weather group. Then FEW110/// — that's the cloud group, but the cloud amount is "FEW" at 11,000 feet, and the type of cloud is replaced by slashes. Here's the key principle: where a field cannot be determined by the automatic station, it is not omitted — it is replaced by a forward slash for each element of the group. So at Lyneham, the visibility, weather, and type of cloud cannot be determined, and those groups have been replaced by a slash for each element. Then we have the temperature and dew point: 09/06 means the temperature is 9°C and the dew point is 6°C. Then Q1023 — that's the QNH, 1023 hPa. And finally, at the very end of the message, we see an equals sign: =. That equals sign denotes that the message is complete. It's the end-of-message marker. Now let me show you a more complete, human-generated METAR to see how all the groups fit together: METAR EGTK 231020Z 26012G25KT 220V300 9999 –RA FEW060 SCT120 10/M02 Q0991 RETS WS ALL RWY NOSIG = Let's walk through it. EGTK is the aerodrome — that's Oxford/Kidlington. 231020Z — the 23rd day of the month at 1020 Zulu. Surface wind: 26012G25KT — wind from 260 degrees at 12 knots, gusting to 25 knots. Then 220V300 — that's the wind direction variability, from 220 to 300 degrees. Then 9999 — that's the visibility, 10 kilometres or more, the maximum reportable value. Then –RA — that's light rain, the minus sign means light intensity. Then FEW060 — a few clouds at 6,000 feet, and SCT120 — scattered clouds at 12,000 feet. Then 10/M02 — temperature 10°C, dew point minus 2°C. Q0991 — QNH 991 hPa. Then RETS — that means recent thunderstorm, a thunderstorm occurred in the last hour but is no longer present. Then WS ALL RWY — wind shear on all runways. And finally NOSIG — no significant change expected in the next two hours, which is the TREND forecast appended to the METAR. The summary point I want to leave you with: although METARs may appear confusing at first, with practice it becomes quite simple to decode them accurately and speedily. As a pilot, you should consult METARs for departure and destination aerodromes, for other aerodromes along your planned route, and particularly for aerodromes upwind of your destination — that gives you a picture of the weather approaching your destination. And if your destination aerodrome does not issue a METAR, consult a METAR from an aerodrome in the vicinity of your destination. Now, the book has practice questions here. Let's try them one at a time.