Useful Aviation Information
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Aeronautical Meteorological Codes
International METAR codes
The following is a sample METAR from OR Tambo International in Johannesburg, South Africa and as if it was taken on 4 July 2005 at 16:00 Coordinated Universal Time (UTC).
METAR FAJS 041600Z 12003KT 310V290 1400 R04/P1500N R22/P1500U +SN BKN022 OVC050 M01/M03 Q1020 NOSIG 03L49//91=
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METAR indicates that this following is a standard hourly observation.
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FAJS is the ICAO airport code for OR Tambo International Airport.
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041600Z is the time of the observation. It is the day of the month (the 4th) followed by the time of day (1600 Zulu time, which equals 4:00 pm Greenwich Mean Time).
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12003KT is the wind direction: 120° (east-southeast) at a speed of 3 KT. Speed measurements can appear as knots (KT) or meters/second (MPS).
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310V290 indicates that the wind direction varies from 310° true (northwest) to 290° true (west-northwest).
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1400 is the prevailing visibility which is 1,400 m (4,600 ft).
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R04/P1500N means that the Runway Visual Range (RVR) along runway 04 is 1,500 m (4,900 ft) and is not expected to change significantly.
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R22/P1500U indicates that the RVR along runway 22 is 1,500 m (4,900 ft) and rising.
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+SN means that snow is falling at a heavy intensity. Precipitation indicators preceded by + are heavy and by - are light.
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BKN022 indicates a broken (BKN) cloud layer at 2,200 ft (670 m) above ground level (AGL). "BKN" or "OVC" specifies the cloud ceiling.
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OVC050 indicates an unbroken cloud layer (overcast) at 5,000 ft (1,500 m) above ground level.
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M01/M03 indicates that the temperature is −1 °C and the dewpoint is −3 °C . An M in front of the number means that the temperature/dew point is below zero (0) degrees Celsius.
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Q1020 refers to the current altimeter setting (QNH) which is 1,020 hPa.
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NOSIG is an example of a TREND forecast which is appended to METARs at stations while a forecaster is on watch. NOSIG means that no significant change is expected in the reported conditions within the next 2 hours.
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03L49//91 refers to the condition of the runway:
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03L is the specific runway.
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4 means that the runway is coated with dry snow.
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9 means that 51% to 100% of the runway is covered.
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// means that the thickness of the coating was either not measurable or it is not affecting usage of the runway.
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91 means that the braking index is bad, and tires will have bad grip on the runway.
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CAVOK (abbreviation for Ceiling And Visibility OKay,) indicates that there is no cloud below 5,000 ft (1,500 m), no cumulonimbus at any level and a visibility of 10 km (6 SM or more and no significant weather. As of 5 November 2008 this has been amended to include towering cumulus
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= indicates the end of the METAR report
Cloud coverage is reported in terms of 'oktas' (eighths) of the sky that are covered by cloud.
This is reported as:
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CLOUD
Cloud amount may be described as:
NSC = 'No (nil) significant cloud' (i.e. none below 5,000 ft (1,500 m) and no TCU or CB)
FEW(few) = 1-2 OKTAS
SCT(scattered) = 3-4 OKTAS
BKN(broken) = 5-7 OKTAS
OVC (overcast) = 8 OKTAS
Note: 1 OKTA = 1/8 cloud cover
Cloud base is given in hundreds of feet above aerodrome level (aal)ft.
Cloud type is not identified, except:
CB = Cumulo-nimbus
TCU = Towering Cumulus
SKC = Sky Clear
NSC = No Significant Cloud (TAF only)
If the sky is obscured the letters VV are inserted followed by the vertical height in hundreds of feet.
VV/// = Sky obscured, vertical visibility cannot be assessed.
CAVOK
(Pronounced KAV-O-KAY) will be used to replace the visibility, RVR, weather and cloud groups if the following conditions apply:
A Visibility: 10km or more
B Cloud: no cloud below 5000ft or below highest Minimum Sector Altitude, whichever is greater and no CB at any height
C No significant weather at or near the airfield
AIR TEMPERATURE/DEWPOINT
These are given in degrees Celsius
M = Minus
QNH
Rounded down to the next whole millibar and given as a four figure group in millibars/hectopascals, preceded by Q. If the value is less than 1000, the first number is 0.
