Help understanding METARs

Profile picture for user EGPH

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13 years 8 months

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Hey all, I hope I have chosen the forum wisely as this could go in either General Disc, Civil Aviation or here mods feel free to move. I have been trying to teach myself to read METARs today as a little project seeing as I am at a loose end for a few days, I think I have most of the basics under my belt but just one figure is annoying me. METAR EGAA 202050Z 34008KT 9999 FEW025 BKN033 12/10 Q1014 SO... I know that its a METAR observation for Belfast Aldergrove made on the 20th at 20:50 GMT and that winds are 340 deg at 8 kts and after the 9999 is cloud info follwed by temperature/dew point info and the QNH however nowhere can I find what the 9999 stands for. Anyone fill me in? Thnaks in advance EGPH
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15 years 7 months

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Visibility is not restricted. Don't expect to see that very often :(
Profile picture for user atr42

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This is the guidance given by the MetOffice. Note copyright is theirs and this is provided just for educational purposes. Apologies to the mods if I've still overstepped the mark. Aerodrome actual weather - METAR and SPECI decode Please note the decodes below incorporate the changes to METAR coding introduced on 5 November 2008. CODE ELEMENT EXAMPLE DECODE NOTES 1 Identification METAR or SPECI METAR METAR METAR — aviation routine report, SPECI — selected special (not from UK civil aerodromes) Location indicator EGLL London Heathrow Station four-letter indicator Date/Time 291020Z 'ten twenty Zulu on the 29th' AUTO A fully automated report with no human intervention AUTO METARS may only be disseminated when an aerodrome is closed or at H24 aerodromes, where the accredited met. observer is on a CAA approved overnight duty break. Users are reminded that reports of visibility, present weather and cloud from automated systems should be treated with caution due to the limitations of the sensors themselves and the spatial area sampled by the sensors. 2 Wind Wind direction/speed 31015G27KT 'three one zero degrees, fifteen knots, max twenty seven knots' Max only given if >= 10KT greater than the mean. VRB = variable. 00000KT = calm. Extreme direction variance 280V350 'varying between two eight zero and three five zero degrees' Variation given in clockwise direction, but only when mean speed is greater than 3 KT. 3 Visibility Prevailing visibility 3200 'three thousand two hundred metres' 0000 = 'less than 50 metres' 9999 = 'ten kilometres or more'. No direction is required. Minimum visibility (in addition to the prevailing visibility if required) 1200SW 'Twelve hundred metres to the south-west' The minimum visibility is also included alongside the prevailing visibility when the visibility in one direction, which is not the prevailing visibility, is less than 1500 metres or less than 50% of the prevailing visibility. A direction is also added as one of the the eight points of the compass. NDV = no directional variation (AUTO METARS only) 4 RVR R27R/1100 'RVR, runway two seven right, one thousand one hunded metres' RVR tendency (U = increasing; D = decreasing; N = no change) may be added after figure (not currently used in the UK) e.g. R27R/1100D. P1500 = more than 1500 m; M0050 = less than 50 m. Significant variations — example : R24/0950V1100, i.e. varying between two values. (Not from UK civil aerodromes) 5 Present weather +SHRA 'heavy rain showers' + = Heavy (well developed in the case of +FC and +PO); - = Light; no qualifier = Moderate. BC=Patches BL=Blowing BR=Mist DR=Drifting DS=Duststorm DU=Dust DZ=Drizzle FC=Funnel cloud FG=Fog FU=Smoke FZ=Freezing GR=Hail (>5mm) GS=Small hail or snow pellets HZ=Haze IC=Ice crystals MI=Shallow PL=Ice pellets PO=Dust devils PR=Banks RA=Rain SA=Sand SH=Showers SG=Snow grains SN=Snow SQ=Squalls SS=Sandstorm TS=Thunderstorm VA=Volcanic ash VC=In vicinity UP=Unidentified precipitation (AUTO METARS only) Up to three groups may be present, constructed by selecting and combining from the above. Group omitted if no weather to report. 6 Cloud FEW005 SCT010CB BKN025 'few at five hundred feet, scattered cumulonimbus at one thousand feet, broken at two thousand five hundred feet' FEW='few' (1-2 oktas), SCT='Scattered' (3-4 oktas), BKN='Broken' (5-7 oktas), OVC='Overcast', NSC= no significant cloud (none below 5000 ft and no TCU or CB). There are only two cloud types reported; TCU=towering cumulus and CB=cumulonimbus. VV///='state of sky obscured' (cloud base not discernable): Figures in lieu of '///' give vertical visibility in hundreds of feet. Up to three, but occasionally more, cloud groups may be reported. Cloud heights are given in feet above airfield height. NCD= no cloud detected (AUTO METARS only) 7 CAVOK* CAVOK 'cav-oh-kay' Visibility greater or equal to 10 km and the lowest visibility is not reported, no cumulonimbus or towering cumulus, no cloud below 5000 ft or highest minimum sector altitude (MSA)( whichever is the greater) and no weather significant to aviation. 8 Temp and dew point 10/03 'temperature ten degrees Celsius, dew point three degrees Celsius' If dew point is missing, example would be reported as 10///. M indicates a negative value 9 QNH Q0995 'nine nine five' Q indicates hectopascals. If the letter A is used QNH is in inches and hundredths. 10 Recent weather RETS 'recent thunderstorm' RE = Recent, weather codes given above. Up to three groups may be present. 11 Wind shear WS RWY24 'wind shear runway two four' Will not be reported at present for UK aerodromes. 12 Colour states Military reports also display a colour state BLU, WHT, GRN, YLO1, YLO2, AMB or RED, coded according to cloud and visibility. BLACK indicates the runway is unusable. 13 Runway state group 24421594 Runway 24 has dry snow covering 11% to 25% of the runway to a depth of 15 millimetres. Braking action is medium or good DRDRCEttBB DRDR is the runway designator: 27 = Runway 27 or 27L; 77 = Runway 27R (50 is added for "right"); 88 = All runways; 99 = A repetition of the last message, because no new information has been received. C indicates runway deposits: 0 = clear and dry; 1 = damp; 2 = wet; 3 = rime or frost covered; 4 = dry snow; 5 = wet snow; 6 = slush; 7 = ice; 8 = compacted or rolled snow; 9 = frozen ruts or ridges; / = not reported due to runway clearance in progress E indicates extent of contamination: 1 = 10% or less; 2 = 11-25%; 5 = 26-50%; 9 = 51-100%; / = not reported due to runway clearance in progress tt indicates depth of contamination: 00 = <1; 01-90 = 1 to 90 mm; 91 not used; 92 = 10 cm; 93 = 15 cm; 94 = 20 cm; 95 = 25 cm; 96 = 30 cm; 97 = 35 cm; 98 = 40 cm or more; 99 = Runways non-operational due to snow clearance; // = not measurable or not significant BB indicates friction coefficient / braking action: 28 = friction coefficient 28%; 35 = friction coefficient 35%; 91 = braking action poor; 92 = braking action medium/poor; 93 = braking action medium; 94 = braking action medium/good; 95 = braking action good; 99 = figures unreliable; // = not reported If the aerodrome is closed due to contamination of runways, the abbreviation SNOCLO is used in place of a runway state group. If contamination ceases to exist, the abbreviation CLRD is used between 88 and braking action. 14 Trend BECMG FM1100 23035G50KT 3000 SHRA 'becoming from 1100, 230 degrees 35 KT , max 50 KT, 3000 metres, moderate rain showers BECMG=Becoming TEMPO=Temporarily NOSIG=No sig change NSW=No sig weather AT=At FM=From TL=Until NSC=No sig cloud Any of the wind, visibility, weather or cloud groups may be used, and CAVOK. Multiple groups may be present. *CAVOK will replace visibility and cloud groups Example SAUK02 EGGY 301220 METAR EGLY 301220Z 24015KT 200V280 8000 —RA FEW010 BKN025 18/15 Q0983 TEMPO 3000 RA BKN008= An example of the above METAR for 1220 UTC on the 30th of the month, in plain language: EGLY: Issued at 1220Z on 30th. Surface wind: mean 240 deg true, 15 KT; varying between 200 and 280 deg; prevailing vis 8 km; light rain; cloud; 1-2 oktas base 1000 ft , 5-7 oktas 2500 ft; temperature +18°C, dew point +15°C QNH 983 hPa; Trend: temporarily 3000 m in moderate rain with 5-7 oktas 800 ft. Example SAUK02 EGGY 301220 METAR EGPZ 301220Z 30025G37KT 270V360 6000 1200NE +SHSN SCT005 BKN010CB 03/M01 Q0999 RETS BECMG AT1300 9999 NSW SCT015= An example of the above METAR for 1220 UTC on the 30th of the month, in plain language: EGPZ: Issued at 1220Z on the 30th. Surface wind: mean 300 deg true, 25 KT; maximum 37 KT, varying between 270 and 360 deg; prevailing vis 6 km, minimum vis 1200 m (to north-east); heavy shower of snow, Cloud; 3-4 oktas base 500 ft , 5-7 oktas CB base 1000 ft, temperature +3°C, dew point -1°C; QNH 999 hPa; Thunderstorm since the previous report; Trend: improving at 1300 Zulu to 10 km or more, nil significant weather, 3-4 oktas 1500 ft.
Profile picture for user EGPH

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Thank you for the prompt replies and the detailed info it is much appreciated
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This is the guidance given by the MetOffice. Note copyright is theirs and this is provided just for educational purposes. Apologies to the mods if I've still overstepped the mark.
No apologies necessary. The information is promulgated for safety purposes, I can't imagine the Met Office would be the least bit fazed by its posting here. Moggy Moderator
Profile picture for user Kenneth

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It is pathetic - and not very conducive to safety - that TAF's and METAR's are still written in this incomprehensible short-hand, which has its roots in the low data bandwidth of the telegraph and telex technology in use when it originated. I see no technical reason for not using plain, English language nowadays, and it would be much safer too.
Profile picture for user Arthur Pewtey

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Maybe so but lots of people understand them - they're not that difficult to comprehend - hardly incomprehensible. If a pilot wants a TAF or METAR printed out on his FMS or ACARS, he doesn't want a long Jackanory story to read, he wants a simple statement that tells him all he needs to know. Which is best for reading over the radio or over a datalink? This LEST 201230Z 21010G25KT 180V250 1200SW 6000NW R17/1300U R35/P1500 +SHRA FEW010CB SCT017 BKN027 12/07 Q1002 RETS WS RWY17 BECMG FM1300 23030G40KT 7000 NSW SKC or Location: LEST Day of month: 20 Time: 12:30 UTC Wind: True direction = 210 degrees, Speed: 10 knots, with Gusts of maximum speed 25 knots Wind direction is variable between 180 and 250 Visibility: 1200 m direction South West Visibility: 6000 m direction North West Runway 17, touchdown zone visual range is variable from a minimum of 1300 meters until a maximum of meters, and increasing Runway 35, touchdown zone visual range is variable from a minimum of more than 1500 meters until a maximum of meters Weather: Strong Showers of Rain Clouds: A few , at 1000 feet above aerodrome level, cumulonimbus Clouds: Scattered , at 1700 feet above aerodrome level Clouds: Broken sky , at 2700 feet above aerodrome level Temperature: 12 degrees Celsius Dewpoint: 07 degrees Celsius QNH (Sea-level pressure): 1002 hPa Since the previous observation (but not at present), the following meteorological phenomena were observed: Thunderstorms There is wind-shear in runway 17 The following weather phenomena are expected to arise soon: From 13:00 UTC, Wind: True direction = 230 degrees, Speed: 30 knots, with Gusts of maximum speed 40 knots Visibility: 7000 m No significant weather phenomena are observed at present Clear sky
Profile picture for user BlueRobin

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I hated them short but now I love them. Once it gets into your head, you can speed read easily. Useful tool on my phone, which wouldn't really look good with a longer format. And that's just METARs. Imagine a plain english TAF with lots of PROB30 TEMPOs due to passing showers?
Profile picture for user Al

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It is pathetic - and not very conducive to safety - that TAF's and METAR's are still written in this incomprehensible short-hand, which has its roots in the low data bandwidth of the telegraph and telex technology in use when it originated. I see no technical reason for not using plain, English language nowadays, and it would be much safer too.
If you are an aviator, it's only unsafe if you are so unprofessional, or so stupid, that you don't know the codes. They are carefully designed to be short and precise, and fit for purpose, which usually includes aircrew walking around with a few sheets of paper in their metpack, and not weighed down by War and Peace...
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They're also language independent

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They're also language independent
Yes, but.... I had to learn to read them in American (vis in SM,pressure in inches, but curiously temps still in Celsius).
Profile picture for user Kenneth

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If you are an aviator, it's only unsafe if you are so unprofessional, or so stupid, that you don't know the codes.
With "incomprehensible" I didn't mean that I can't read them. I meant that you need to known the short-hand first. Yes, I am an aviator (PPL-A, 3-axis microlight, + 20 years experience - accident free). Who the h*ll do you think you are to rate me as being "unprofessional" and "stupid"? Are you a pilot? No, probably not because if you were then you would know that there are other ways acquiring wx info that may be more appropriate/precise depending on where you fly, and from country to country.
Profile picture for user Arthur Pewtey

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I am at loss to understand this. You are a PPL with 20 years experience and find METAR and TAF decoding "incomprehensible"? Of course you need to know the short-hand, same as you need to know the "short-hand" for QNH or VOR or ILS or air traffic clearances etc. Aviation is full of abbreviations and short-hand through necessity - learning to interpret the "incomprehensible" is (or should be) part of your training.
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I am at loss to understand this.
No need, re-read the two first sentences in my last post. I can read them, but only because I first learned it and then have kept in practice. If you didn't learn them properly (i.e. only enough to pass the tests, maybe with a bit of luck) and/or haven't kept in practice, then the style in which they're written is a potential source for misinterpreted weather info. And that is where I see the problems. Moreover, the extent to which you use them (and hence to some extent the degree of direct practice you get) is also dependent on the type of flying you do. METAR/TAF's may not be the best weather briefing you can get, if your jolly takes place far away from any airports for which these are drawn up. I maintain that there is room for improvement in the form in which these are drawn up. The generally accepted ultra-conservative stance is the bane of aviation, particularly general aviation. Nothing will progress to the better if we simply sit down and accept what we have, instead challenging it and seeing where improvements can be made. As regards the "paper", the current trend is away from this and towards electronic media. For example, I met someone the other day who amongst others has the entire AIP for Germany on his Ipad, for which he also has a cockpit mount. As regards plain language, I didn't mean
Wind: True direction = 210 degrees, Speed: 10 knots, with Gusts of maximum speed 25 knots
but something along the lines of
Wind 210 degrees 10 knots, gusts up to 25 knots
as you for example get them on an ATIS. As regards abbreviations in general: ATC clearances are issued orally in the form of a standard phraseology, not abbreviations. I don't need to know what VOR and ILS are abbreviations of, I need to know what they are and what they do. All of the Q-codes are, as far as I know, not abbreviations of anything, but are designed to be easy to write in Morse. While the rest of the world has discarded Morse, it remains in aviation. So much for coming with new ideas (although in this particular case I accept them as poignant expressions which are easy to remember, and for which I don't see a pressing need for replacement). Finally, the METAR/TAF's are not language independent, as the weather phenomena are abbreviations of English expression. A language in which every pilot has to prove proficiency in these days, if you want to use it on the R/T. So that point is moot.
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Wind 210 degrees 10 knots, gusts up to 25 knots
So why do you find 21010G25 so difficult? I'm not a pilot, I haven't flown professionally for 5 years and yet I can interpret a METAR easily. If ATC says "QNH 1004", I take it you would prefer if they said "please set your altimeter to a Barometric setting of 1004 Hectopascals. This will read the height of the airfield above sea level when you land" That would be much simpler? By the way, the Q codes did mean something although the actual meanings have been lost now.
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I'm not getting across to you, am I?
So why do you find 21010G25 so difficult?
I don't, it was only an example, challenging your proposed write up. I would like to see something like "recent thundershowers" instead of "RETS". This as an example only
If ATC says "QNH 1004", I take it you would prefer if they said "please set your altimeter to a Barometric setting of 1004 Hectopascals. This will read the height of the airfield above sea level when you land" That would be much simpler?
No and no; I have no problems with the Q-codes (see above).
Profile picture for user Arthur Pewtey

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It is pathetic - and not very conducive to safety - that TAF's and METAR's are still written in this incomprehensible short-hand, which has its roots in the low data bandwidth of the telegraph and telex technology in use when it originated. I see no technical reason for not using plain, English language nowadays, and it would be much safer too.
That was your original post - now you're backtracking and saying that you understood it anyway :confused: I don't understand why you would want only weather in plain langauge but everything else seems to be OK with abbreviations and codes.
Profile picture for user Kenneth

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I gv up - thx & c u ;)

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Moreover, the extent to which you use them (and hence to some extent the degree of direct practice you get) is also dependent on the type of flying you do. METAR/TAF's may not be the best weather briefing you can get, if your jolly takes place far away from any airports for which these are drawn up.
In which case other sources such as low-level forecasts, VFR charts, SWCs, wind tables and ordinary weather forecasts (whichever applicable) can be used. I think a few pilots would agree that especially SWCs can be improved. Personally I prefer the Nordic SWC (for flying in that area).
I maintain that there is room for improvement in the form in which these are drawn up. The generally accepted ultra-conservative stance is the bane of aviation, particularly general aviation. Nothing will progress to the better if we simply sit down and accept what we have, instead challenging it and seeing where improvements can be made.
I can partially agree on this. Not sure if it's the "bane of aviation" as you put it, but I also think maybe some accepted "truths"/standards should be challenged now and then for the better.