What is METAR (Meteorological Aviation Report)? (To prepare for RTR(A) part 2 and also useful info for met paper)
Aviation Weather Report (METAR/SPECI)
METAR is a format for reporting weather information. A METAR weather report is predominantly used by pilots in fulfillment of a part of a pre-flight weather briefing, and by meteorologists, who use aggregated METAR information to assist in weather forecasting.
Raw METAR is the most common format in the world for the transmission of observational weather data. It is highly standardized through the International Civil Aviation Organization (ICAO), which allows it to be understood throughout most of the world.
METAR is an aviation routine weather report issued at hourly or half-hourly intervals. It is a description of the meteorological elements observed at an airport at a specific time.
SPECI is an aviation special weather report issued when there is significant deterioration or improvement in airport weather conditions, such as significant changes of surface winds, visibility, cloud base height and occurrence of severe weather. The format of the SPECI report is similar to that of the METAR and the elements used have the same meaning. The identifier METAR or SPECI at the beginning of the weather report differentiates them.
The aviation weather report also includes a section containing the trend forecast, which indicates the forecast change in meteorological conditions in the next two hours.
Information contained in a METAR
A typical METAR contains data for the temperature, dew point, wind speed and direction, precipitation, cloud cover and heights, visibility, and barometric pressure. A METAR may also contain information on precipitation amounts, lightning, and other information that would be of interest to pilots or meteorologists such as a pilot report or PIREP, colour states and runway visual range (RVR).
In addition, a short period forecast called a TREND may be added at the end of the METAR covering likely changes in weather conditions in the two hours following the observation. These are in the same format as a Terminal Aerodrome Forecast (TAF).
The complement to METARs, reporting forecast weather rather than current weather, are TAFs. METARs and TAFs are used in VOLMET broadcasts.
Cloud coverage is reported by the number of ‘oktas’ (eighths) of the sky that is occupied by cloud.
This is reported as:
|SKC||“No cloud/Sky clear” used worldwide but in North America is used to indicate a human generated repor|
|CLR||“No clouds below 12,000 ft (3,700 m) (U.S.) or 10,000 ft (3,000 m) (Canada)”, used mainly within North America and indicates a station that is at least partly automated|
|NSC||“No (nil) significant cloud”, i.e., none below 5,000 ft (1,500 m) and no TCU or CB. Not used in North America.|
|FEW||“Few” = 1–2 oktas|
|SCT||“Scattered” = 3–4 oktas|
|BKN||“Broken” = 5–7 oktas|
|OVC||“Overcast” = 8 oktas, i.e., full cloud coverage|
|VV||Clouds cannot be seen because of fog or heavy precipitation, so vertical visibility is given instead.|
METAR WX codes
METAR abbreviations used in the WX section. Remarks section will also include began and end times of the weather events.
Codes before remarks will be listed as “-RA” for “light rain”. Codes listed after remarks may be listed as “RAB15E25” for “Rain began at 15 minutes after the top of the last hour and ended at 25 minutes after the top of the last hour.”
|Intensity||–||Light intensity||blank||Moderate intensity|
|Intensity||+||Heavy intensity||VC||In the vicinity|
|Precipitation||IC||Ice Crystals||PL||Ice Pellets|
|Precipitation||GR||Hail||GS||Small Hail and/or Snow Pellets|
|Other||SQ||Squall||PO||Dust or Sand Whirls|
|Time||B||Began At Time||E||Ended At Time|
|Time||2 digits||Minutes of current hour||4 digits||Hour/Minutes Zulu Time|
|The latest aviation weather report at the Ahmedabad International Airport issued by the Ahmedabad Observatory at 15:30 LT on 13 Jul 15METAR VAAH 130730Z 35005KT 310V050 9999 FEW025 34/25 Q1000 NOSIG=|
Decoded METAR/SPECI in plain language:-
Aviation weather report (METAR) at 0730 UTC on 13 Jul 2015 issued by the Ahmedabad Observatory :
|Wind||Visibility||Weather||Cloud Amount||Cloud Base||Temperature||Dew Point||Pressure(QNH)|
|5 knots from 350 degrees (N), variability: 310-050 degrees||
10 km or above
|No significant weather||
|Next Two Hours Change|
|No Significant Change|