Metars and TAFs

By David Bartlam

Important Terms

  • METAR – Acronym for Meteorological Aerodrome Report
  • TAF – Terminal Aerodrome Forecast
  • AGL – Above Ground Level
  • MSL – Mean Sea level

For more information on types of altitude see AirplanesAirspeedsAltitudes – by Eric Sterns

Introduction

What is a METAR, SPECI,TREND,TAF and RAFOR? Its good to have a base understanding of Metars to further enhance your knowledge and gameplay. After reading this, you should be able to decipher any one of these.

Metar:
Aerodrome meterological report to which a TREND forecast may be added. Updated at ten minutes to every hour at Military stations and at 10 minutes to and 20 minutes past each hour and civil stations.
Auto Metar: Fully automated weather report generated without human intervention. Often used when airfield is closed. Much less accurate.
Speci: Special aerodrome weather report issued following a significant change from the previous report. Civil airfields do not use these.
Trend: A forecast showing significant changes expected in the 2 hours following a metar or speci.
TAF Terminal Aerodrome Information.

A forecast of conditions and significant changes expected during a specified period, normally 9 hours but may be up to 30 hours. Issued every 3 hours until the airfield closes.
Rafor: Forecasts for certain NATO military air weapon ranges issued in TAF code. Issued every 3 hours until range closure.

Format of METAR, SPECI and TRENDs in the UK

a) Location: eg EGBB, EHAM

b) Date/Time of report: The day of the month and time of observation in hours and minutes UTC. eg 190660Z

c) AUTO Indicates that the metar has been generated with no human input. If an element cant be observed, it will be replaced with slashes. e.g //// for visibility ///////// for cloud

d) Surface Wind The mean wind direction in degrees true to the nearest 10 degrees, from which the wind is blowing and the mean wind speed in knots. eg 35015KT = 350° @ 15KTs. VRB05KT = variable at 5KTs. 00000=Calm. If gusts exceed the mean wind speed by 10 knots or more in the 10 minutes preceding the time of report, a letter G and two more figures are added to indicate max wind speed. e.g 23018G30KT = 230° @ 18kts with a maximum of 30kts.
Reports from outside the UK may express wind speed in Metres per second (MPS) or Kilometers per hour (KPH). Winds greater than 100KTS or more shall be preceded by the letter P.
At civil aerodromes the wind direction may be expressed as variable, express by the letter V. eg 130V230

e) Visibility: reported in a 4 figure group e.g 0400 = 400m, 8000=8KM up to but excluding 10km; 9999 = 10km or more, 0000 = less than 50m. The visibility readings differ slightly for military aviation, I wont type the differences but if anyone wants to know, feel free to ask.

f) Runway Visual Range (RVR) Civil aerodromes may include the letter R followed by runway designator, a ‘/’ and the touchdown zone RVRV in metres, eg R06/0400. If the RVR is assessed on 2 or more runways, the RVR group will be repeated. Parrallel runways will have L,C or R (Left, Centre or Right) added to the designator e.g R08L/1100 R08R/1150. More information on designators is available, just ask.

g) Weather Weather is indicated by up to three groups comprising symbols and letters from the following
– = Slight
+ = Heavy
BC = Patches
BL = Blowing
BR = Mist
DR = Low drifting
DS = Dust storm
DU = widespread dust
DZ = Drizzle
FC = Funnel Cloud (Tornado)
FG = Fog
FU = Smoke
FZ = Freezing
GR = Hail
GS = small Hail
HZ = Haze
IC = Diamond Dust
MI = Shallow
Pl = Ice Pellets
PO = dust Devils
RA = Rain
SA = Sand
SG = Snow Grains
SH = Shower
Sn = Snow
SQ = Squall
SS = Sandstorm
TS = Thunderstorm
VA = Volcanic Ash
VC = In the vicinity
PR (Part covering of aerodrome) may be used in conjunction with FG instead of BC. The symbols – and + are used to signal the intensity. Weather or moderate intensity has no qualifier e.g RASN = moderate rain and snow, + SHRASN = Heavy shower of rain and snow. -FZDZ = slight freezing drizzle.
Civil aerdromes will not report BR, HZ, FU, IC, DU and SA when visibility is greater than 5000m
There is more information on weather in AUTO Metars. Please ask if you want to know.

H) Cloud Cloud amount is reported as: Few (1-2 oktas), scattered (3-4 oktas), broken (5-7 oktas) or overcast (8 oktas) using FEW, SCT, BKN and OVC, followed by the height of the cloud base in hundreds of feet above aerodrome elevation e.g SCT018 = scattered at 1800ft.
At military aerodromes there are no height restrictions on the cloud that can be reported in a METAR. At civil aerodromes cloud information will be limited to cloud of operational significance i.e cloud below 5000ft or the highest minimum sector altitude and CB Cumulonimbus and TCU towering cumulus e.g SCT018CB = scattered cumulonimbus at 1800ft. Cloud type information is not available in auto observations .
Cloud is reported from lowest base to highest. Sky obscured is annotates as VV followed by vertical visibility in hundreds of feet.
When there are no clouds to report, no CB, TCU and CAVOK is not appropriate, the abbreviation NSC (No significant Cloud) will be used. NCD is used when No Cloud Detected

I) CAVOK  The visibility, cloud and weather groups are replaced by the term CAVOK (Ceiling and visibility OK) when the following conditions exists:
1) Prevailing visibility is 10km or more
2) No minimum visibility reported
3) No cloud below 5000ft or below minimum sector altitude
4) No CB or TCU at any height
5) No significant weather in aerodrome vicinity

J) Temperature Air temperature and dew point are reported in whole degrees Celsius eg. 10/07 (air temperature 10°c dew point 07°C. Temperatures below 0°C are indicated as M e.g M01/M03 means air teperature -1°C Dew point -3°C

K) QNH QNH is stated to the nearest whole hectopascal (Equivalent to a milibar) rounded down and preceded by the letter Q. Q1013 = QNH 1013hPa

L) Recent Weather Significant weather observed in the period since the last routine observation will be reported by using the code letters for weather preceded by the letters RE. eg RETS means Recent thunderstorm

M) Wind Shear In a Metar, civil aerodromes may include wind shear if reported along the take off or approach paths in the lowest 1600ft with reference to the runway. WSb] is used to begin the group. e.g WS TKOF RWAY20

N) Colour State – military aerodromes use a colour coding system to replicate information. Please ask if you want more details

O) Runway State Group An 8 figure group which may be added to the METAR from civil aerdromes
1) Rway designator (First two digits)
27 = Rwy 27 or 27L
77 = Rway 27R (50 added to the designator for “right” rwy)
88 = all rwys
99 = Repetition of the last message as no new information recieved.

2) Rwy deposits (third digit)
0 = Clear and dry
1 = Damp
2 = Wet or water patches
3 = Rime or frost covered
4 = Dry Snow
5 = Wet Snow
6 = Slush
7 = Ice
8 = Compacted snow
9 = Frozen ruts or ridges
/ = Type of deposit not reported

3) Extent of contamination (Fourth digit)
1 = 10% or less
2 = 11% t0 25%
5 = 26% to 50%
9 = 51% to 100%
/ = Not rerported

4) Depth of deposit (Fifth and sixth digits). The quoted depth is the mean of a number of readings or greatest depth measured
00 = Less than 1mm
01 = 1mm etc. to 90 = 90mm
91 = not used
92 = 10cm
93 = 15cm
94 = 20cm
95 = 25cm
96 = 30cm
97 = 35cm
98 = 40cm or more
// = Not significant or measureable

5) Friction coefficient or braking action (seventh and eigth digits)
28 = friction coefficient 0.28
35 = Friction coefficient 0.35 or :
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

P) TREND 
Trend forecasts are indicated BECMG (Becoming) or TEMPO (temporary) which may be followed by a time group (Hours and minutes UTC) preceded by the letter indicators FM (From), TL (Until), AT (at). E.g BECMG FR1030 TL1130 (Becoming From 1030 until 1130)
NOSIG replaces the TREND group when there are no significant changes taken places within the next 2 hour forecasting period
To indicate the end of significant weather, NSW is used

And there you have it, a detailed introduction into reading METARS etc. I will now post some METARS below, have a go at deciphering them! For an extra challenge, I will put 2 military METARS up.. Research and tell me what they mean. Enjoy

EGPH 141320Z 06009KT 6000 OVC011 04/03 Q0981

EHAM 141325Z 12018KT 090V150 CAVOK 05/03 Q0991 NOSIG

EDDT 141320Z 12009KT 8000 BKN060 M01/M03 Q1008 R88L/190095 R08R/290195 NOSIG

EGDR 141250Z 26010G21KT 9999 VCSH FEW008 SCT018 BKN028 09/08 Q0977 RERA WHT TEMPO 4000 SHRA SCT007 BKN014 GRN

EIDW 141300Z 13014KT 6000 -RADZ SCT003 BKN005 BKN010 07/07 Q0972 TEMPO 3000

BGSF 141320Z AUTO VRB02KT 9999NDV NCD M08/M09 Q0999-

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