Decoding a MEteorological Terminal Air Report (METAR)
An example:
KPIT 201155Z COR 22015G25KT 3/4SM R28R/2600FT TSRA OVC010CB 18/16 A2992 RMK TSB09RAB28 OCNL LTGCCCG VC NE TS VC NE MOV NW SLP132 P0023 60057 70122 T01780156 10211 20178 53010
Note: When a particular weather element is not applicable or not available, it is omitted from the METAR.
KPIT is the ICAO station identifier. For continental US stations, the first letter is always K, followed by the perhaps more familiar three-letter airport code. In this case, the observation is from Pittsburgh.
201155Z means the observation was taken on the 20th of the month at 1155 UTC. This would commonly be referred to as the “12Z report.” Observations are often taken hourly around 50 to 59 minutes after the hour. More frequent observations may be warranted if weather conditions are rapidly changing.
COR indicates this report is a CORrection of a previous report. You may also see AUTO here, indicating the observation was AUTOmated. Or you may see neither.
22015G25KT is the wind observation. The wind is from 220° and has a speed of 15 knots, Gusting to 25 KnoTs. Other possible indications of the wind include 00000
KT if it is calm, VRB for variable wind direction, and 180V260 to indicate, for instance, that the wind is varying between 180° and 260°.
3/4SM means the visibility is ¾ Statute Miles.
R28R/2600FT is an indication of the Runway Visual Range. In this case, Runway “28 Right” has a visual range of 2600 FeeT.
Next is the current significant weather, if any. In this case, TSRA (moderate rain with thunder) is observed.
Intensity is indicated by a prefix:
Minus sign à Light
No sign à Moderate
Plus sign à Heavy
Abbreviations for this section include:
RA Rain DZ Drizzle SN Snow
SG Snow Grains IC Ice Crystals PE/PL Ice Pellets
GR Hail (gréle) GS Snow Pellets (grésil) UP Unknown Precip.
FG Fog BR Mist (brume) FU Smoke (fumée)
VA Volcanic Ash DU Dust SA Sand
HZ Haze
SH Shower (with SN, RA, PE, GR, GS only)
TS Thunderstorm
FZ Freezing (with RA, DZ, FG only)
MI Shallow (mince) (with FG only)
BC Patches (banc) (with FG only)
PR Partial (with FG only)
DR Drifting (with SN, DU, SA only)
BL Blowing (with SN, DU, SA only)
SQ Squalls PO Dust Devil +FC Tornado/Waterspout
FC Funnel Cloud SS Sandstorm DS Duststorm
Next comes the cloud section. In this case, OVC010CB means the sky is overcast with cumulonimbus at 1000 feet. Cloud base is reported in hundreds of feet, and if Towering CUmulus or CumulonimBus are present, TCU or CB will be reported.
More than one cloud layer may be reported. Clouds are characterized based on eighths (octas) of the sky:
SKC Sky Clear
CLR Sky Clear below 12,000 feet
FEW 1–2 octas
SCT 3–4 octas
BKN 5–7 octas
OVC 8 octas
VV may be listed here instead if the sky is obscured. VV004 would indicate the Vertical Visibility is 400 feet.
18/16 means the temperature is 18°C and the dewpoint is 16°C. The number is preceded by M for negative readings.
A2992 gives the altimeter setting as 29.92 inches of mercury. Outside the US, this would be reported as Q1013, indicating 1013 hPa (or 1013 mb).
Finally, there is the remark section.
TSB09RAB28 tells us the thunder began 9 minutes after the hour, while rain began to fall 28 minutes after the hour.
OCNL LTGCCCG VC NE indicates that there is occasional lightning both from cloud to cloud (CC) and cloud to ground (CG) in the vicinity (VC) and to the northeast.
TS VC NE MOV NW indicates that a thunderstorm is in the vicinity and to the northeast that is moving northwestward.
SLP132 indicates the sea-level pressure is 1013.2 hPa.
P0023 indicates 0.23″ of precipitation have fallen in the last hour. Other possibilities include P0000 for a trace of precipitation, or nothing at all if there was no precipitation.
60057 (The 6 group) indicates 0.57″ of precipitation have fallen in the past 6 hours. 60000 would refer to a trace, and the lack of a 6 group means there was no precipitation at all. This group only appears in the 00, 06, 12, and 18 UTC observations.
70122 (The 7 group) indicates 1.22″ of precipitation has fallen in the past 24 hours. Only appears once a day, typically around 12 UTC.
T01780156 gives the temperature and dewpoint in Celsius with enough precision to be converted to the nearest whole degree Fahrenheit. So, the temperature was 64°F, while the dewpoint was 60°F (not 60.1!).
10211 (The 1 group) reports the six-hour maximum temperature, again in Celsius with enough precision to be converted to the nearest whole degree Fahrenheit. In this case, it was 70°F.
20178 (The 2 group) is the same as the 1 group but for six-hour minimum temperature.
The 1 and 2 groups are critical for forecast verification, since the high and/or low may occur between routine hourly observations.
If the second digit in the T, 1, or 2 groups is a 1, the temperature is negative.
53010 (The 5 group) contains pressure tendency information. In this case, the pressure has risen 1 hPa in the past three hours. See the pressure tendency handout for information.