METAR, SPECI and TREND
Meteorology · Chapter 25 · DGCA CPL and ATPL
How the weather at an airport is squeezed into one coded line every half hour, and how to read it back as a picture.
Remember
- METAR (routine, half-hourly or hourly) and SPECI (any time a criterion is met) use the same code: type, station, ddhhmmZ, wind, vis, RVR, wx, cloud, T/Td, QNH, RE, WS, TREND.
- Wind: VRB < 3 kt or swinging ≥ 180°; 00000KT calm; G when ≥ 10 kt above mean; dddVddd for 60-180° with ≥ 3 kt; P99 ≥ 100 kt.
- Vis steps 50 m (to 800), 100 m (to 5000), 1 km; 9999 = 10 km+. RVR when vis or RVR < 1500 m; steps 25/50/100 m; U D N, P M.
- Cloud: lowest any, next ≥ 3/8, next ≥ 5/8, plus CB. Bases above aerodrome, 30 m steps to 3000 m. Temps .5 up (−2.5 → M02); QNH down.
- FG < 1000 m, BR 1000-5000 m, HZ/DU/SA/FU/VA ≤ 5000 m. VC within 8 km. FZ only RA/DZ; MI BC PR only FG; DR < 2 m, BL ≥ 2 m.
- CAVOK: vis 10 km+, no cloud below 1500 m/MSA and no CB, no significant weather. MSA: 300 m clearance within 25 NM.
- SPECI: vis 800/1500/3000/5000; RVR 150/350/600/800; BKN/OVC 30/60/150/300/450 m; +2 °C; worse at once, better after 10 min. TREND 2 h, TEMPO < 1 h each and < half.
What does each group of a METAR mean?
A METAR, group by group
A model METAR, decoded one group at a time, in the order it is written. Tap Next.
- Who, where, when METAR is the routine weather report from an aerodrome, sent every half hour or hour. VIDP is the ICAO code for Delhi. 200700Z: the 20th of the month at 0700 UTC ("Zulu"). Add 5 h 30 min for Indian time: 1230 IST.
- Wind 11007G20KT: from 110° true at 7 kt, gusting to 20 kt. A gust is reported when it is 10 kt or more above the mean. 090V160: the direction keeps changing between 090° and 160°.
- Visibility 1400: the prevailing visibility is 1400 m, how far you can see over most of the area round the aerodrome. 9999 means 10 km or more. At 1400 m a pilot sees the ground only a short way ahead, so this is a poor day. Below 1500 m the report must also give the RVR, the next group.
- RVR R28/1100: the runway visual range on runway 28 is 1100 m. It is given only when the visibility or the RVR is below 1500 m.
- Weather +SHRA: heavy (+) showers (SH) of rain (RA). A minus sign means light; no sign means moderate.
- Cloud Amount in octas (FEW 1-2, SCT 3-4, BKN 5-7, OVC 8), then the base in hundreds of feet above the aerodrome: SCT010 is 3-4 octas at 1000 ft. CB (or TCU) is added after the height. Careful: this model breaks a rule. After a BKN layer, a higher layer is reported only if it is BKN or OVC, so FEW030 could not appear there.
- Temperature / dew point 33/26: air 33 °C, dew point 26 °C. Below zero the figure takes an M for minus: 10/M02.
- QNH Q1008: QNH 1008 hPa. It is always rounded down and always has four figures (Q0996). In inches it would be written A2992.
- TREND NOSIG: no significant change expected in the next 2 hours. The = marks the end of the report.
Memory hook: Who-where-when · wind · vis · RVR · wx · cloud · T/Td · Q · trend.
Takeaway: A METAR always runs in the same order: type, station, date and time (UTC), wind, visibility, RVR, weather, cloud, temperature/dew point, QNH, then any extras (RE recent weather, WS wind shear) and the TREND.
In what order are the groups written?
The order
Fly along a METAR, group by group, the way the teacher splits it.
- Type METAR or SPECI Routine report, or special report between routine ones.
- Station VIDP ICAO four-letter code: VIDP Delhi, VABB Mumbai, VECC Kolkata, VOMM Chennai.
- Day and time 200700Z Day of the month and UTC. Add 5 h 30 min for IST: 0700Z is 1230 IST.
- Wind 11007G20KT 090V160 Direction (true) and speed, gusts, and the extremes of a varying direction.
- Visibility 1400 In metres. 9999 = 10 km or more.
- RVR R28/1100 Only when the visibility or RVR is below 1500 m.
- Weather +SHRA Intensity, descriptor, phenomenon.
- Cloud SCT010 BKN020 Amount and base in hundreds of feet above the aerodrome. Or VV, NSC, SKC.
- Temp / dew point 33/26 Whole °C; M for minus.
- QNH Q1008 Rounded down to a whole hPa.
- Extras RETS, WS RWY28 Recent weather and wind shear.
- TREND NOSIG, TEMPO, BECMG The landing forecast for the next 2 hours. Then = ends the report.
Takeaway: Type · station · time · wind · visibility · RVR · weather · cloud · T/Td · QNH · RE · WS · TREND.
What is the weather at Delhi right now?
Read a METAR
Pick a report, then tap any group: the teacher's model and worked examples (given a day where needed).
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What does this foggy-morning METAR actually look like?
Fly into the METAR
The aerodrome as the METAR describes it, group by group. Heights stretched (1 grid step = 1000 ft). Drag to turn it.
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Which METAR fits the sky?
Match the sky to the METAR
Four real satellite days over India. For each, pick the report that fits. (The reports are typical examples written for practice, not the actual reports of those days.)
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How is every kind of wind coded?
The wind group
One compass, six kinds of wind group. Watch each one, then tap Next.
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How are visibility and RVR written?
Visibility and RVR
The visibility steps, visibility by direction, and runway visual range. Tap Next.
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How do you build a weather code like +TSRA?
Weather codes
Build a weather group from left to right: intensity, descriptor, then the weather. Tap Next.
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Which cloud layers make it into a METAR?
The cloud groups
Build the sky layer by layer, using the reporting rule. Tap Next.
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The numbers behind every group
Reporting rules
Tap a card for the detail.
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Can you tell what each group is?
Which group?
Tap a group, then what it reports.
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When can a METAR just say CAVOK?
CAVOK
The three conditions, what CAVOK replaces, and the minimum sector altitude it depends on. Tap Next.
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What changes trigger a SPECI?
When a SPECI goes out
A SPECI is a special report sent between the routine ones. Each picture shows a change that triggers one. Tap Next.
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Will the met office issue a SPECI?
SPECI or not?
Each change is from the last report. Tap it, then decide.
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What does the end of a METAR forecast?
The TREND
An example TREND on a 2-hour timeline, from a METAR at 0800Z. Tap Next.
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Look-alikes in a METAR
Don't mix up
Each pair looks alike. The rule underneath tells them apart.
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Quick test
10 questions to check this chapter. Each answer explains why.
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