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Decoding and Understanding METARs

Updated: Dec 9, 2024




​Aviation Routine Weather Report (METAR) gives an update on the current weather at a specific airport. For student pilots or rusty pilots who haven’t flown in a while, METARs can seem like a foreign language and hard to understand. While many pilots appreciate the decoded version, it is essential for all pilots to learn how to read the METAR/SPECI themselves, especially in cases where a decoded version is not provided.


There are hundreds of METAR’s you can find online by searching for any airport. The primary source of searching METARs, is by going to aviationweather.gov. Other sources are:


METARs are issued, usually 55-59 minutes past the hour, and are valid for one hour or until a new one is released.



Lets go ahead and break it down using our sample METAR.


Sample METAR:

KPDX 301453Z 12015G19KT 10SM FEW010 FEW050 BKN110 09/03 A2987 RMK AO2 SLP115 T00940028 58018


KPDX – Station identifier or airfield, Portland International Airport, Oregon. The station identifier, in International Civil Aeronautical Organization (ICAO) format, is included in all reports to identify the station to which the coded report applies. The ICAO airport code is a four-letter alphanumeric code designating each airport around the world. The ICAO codes are used for flight planning by pilots and airline operation departments.

  • K – Is used for the lower 48 states in the U.S. i.e. KLAX (Los Angeles), KSAN (San Diego), KORD (Chicago O’Hare), etc. Other U.S. station identifiers are; PA – Alaska, PH – Hawaii Islands, PG – Guam.


Special METAR Report:

Aviation Selected Special Weather Report (SPECI) is an unscheduled report taken when any significate change in weather is observed during the period between hourly reports. SPECIs contain all data elements found in a METAR. All SPECIs are issued as soon as possible when relevant criteria are observed.


SPECI KDEN 041635Z 36008KT 10SM R28L/2600FT FEW090 FEW140 BKN220 23/10 A3015 RMK AO2 SLP143 VIRGA NE T00391072



301453Z – Date and Time the report came out. 30 is the day of the month, and 1453 is the time always in Zulu time (UTC).​ The observation times are presented in Zulu time, not local time. This distinction is key to understanding the information accurately.


Report Modifier (AUTO) - The report modifier AUTO identifies the METAR/SPECI as a fully automated report. When the modifier “COR” is used, it” is substituted for “AUTO.” it identifies a corrected report sent out to replace an earlier report that contained an error.


KONT 161053Z COR 25004KT 9SM SCT018 BKN035 BKN050 17/15 A2984 RMK AO2 SLP094 T01720150



12015G19KT – Wind conditions in direction and speed. He wind is blow from 120 degrees true, at a speed of 15 Knots. NOTE: The wind direction is indicated in true heading, not magnetic heading.

  • Winds are gusting it is indicated by the “G”, gusting up to 19 knots.

  • If the winds are inconsistent a VRB in place of the direction will indicate that it is “variable.”

  • Little to no wind a “00000” will appear. 


10SM - Surface visibility is in statute miles (SM). A space is coded between whole numbers and fractions of reportable visibility values. For example, a visibility of 1½SM is coded 1 1/2SM. U.S. automated stations use an M to indicate “less than.” For example, M1/4SM means a visibility of less than ¼SM.


FEW010  FEW050  BKN110  - Cloud cover (FEW010) is few at 1,000 feet AGL, few at 5,000 feet, and broken (BKN) at 11,000 feet AGL. Sky condition group is a description of the appearance of the sky. It includes cloud cover, vertical visibility, or clear skies. You may also see SCT (scattered) or OVC (overcast).

  • Vertical visibility is coded as VV, followed by the vertical visibility into the indefinite ceiling. An “indefinite ceiling” is a ceiling classification applied when the reported ceiling value represents the vertical visibility upward into surface-based obscuration.

  • Clear skies are coded in the format SKC or CLR. When SKC is used, an observer indicates no layers are present; CLR is used by automated stations to indicate no layers are detected at or below 12,000ft.

  • Cumulonimbus (CB) or towering cumulus (TCU) is appended to the associated layer. For example, a scattered layer of towering cumulus at 1,500ft. would be coded SCT015TCU, and would be followed by a space if there were additional higher layers to code.


09/03 – Temperature and Dewpoint are in Celsius (°C). In this example the temperature is 09°C and the dewpoint is 03°C.

  • If the temperatures and/or dewpoint is below freezing, it is prefixed with an M. For example, a temperature of 4°C with a dewpoint of -2°C would be coded as 04/M02; a temperature of -2°C would be coded as M02.


A2987 – Current altimeter setting, 29.87". The “A” is the giveaway, as you’ll use it to set your altimeter. This setting is then used by aircraft altimeters to determine the true altitude above a fixed plane of MSL, in this case pressure altitude.



RMK AO2 SLP115 T00940028 58018  – additional detailed information, which can give a more complete picture of weather conditions but can also be a little more difficult to decipher, at least for a beginner. This part will require a little more memorization or keeping a guide handy to consult. But in this case, here’s what everything means:


RMK indicates “Remarks.” When no remarks are necessary, the contraction RMK is not used.


AO2 or AO1 - Type of Automated Station

  • AO2 - means it is an automated station with a precipitation sensor. It can distinguish between different types of precipitation such as rain, snow, and hail.

  • AO1 - is an automated station, but with no precipitation sensor. That means it cannot distinguish between different types of precipitation.


SLP115 - the ‘sea level pressure” is 1011.5mb. 


T00940028 - is the hourly temperature and dewpoint in detail. In the example the temperature is 09.4°C and the dewpoint is 02.8°C.


58018 – Pressure has fallen 01.8mb. 3 hour pressure tendency. Follows RMK with 5 digits starting with 5. The second digit gives the tendency. In general 0–3 is rising, 4 is steady and 5–8 is falling. The last 3 digits give the pressure change in tenths of a millibar in the last 3 hours.




Other Common Symbols

Here are some common codes you will frequently see on METAR reports. If you want to learn more about different codes, you can find additional information in:


$ - Maintenance indicator is coded when an automated system detects that maintenance is needed on the system.


-RA - Light rain (the minus symbol means light, RA is for rain). Precipitation is any form of water particle, whether liquid or solid, such as; drizzle, rain, snow, etc.


BR - Mist. Obscurations are any phenomenon in the atmosphere, other than precipitation, that reduces the horizontal visibility in the atmosphere, such as; mist, haze, fog, smoke, etc.


CB - Cumulonimbus not associated with thunderstorms is coded, followed by the direction from the station, and the direction of movement, when known. For example, a cumulonimbus up to 10SM west of the station moving toward the east would be coded CB W MOV E. If the cumulonimbus was more than 10SM to the west, the remark is coded CB DSNT W.


TCU - Towering cumulus clouds, followed by the direction from the station. The cloud type and direction entries are separated by a space. For example, a towering cumulus cloud up to 10SM west of the station is coded TCU W.


PK WND – means Peak wind. For example, a peak wind of 45kt from 280° that occurred at 15 minutes past the hour is coded PK WND 28045/15.


VIRGA - precipitation is evaporating before reaching the ground. It is coded as "VIRGA (DIR)", where "VIRGA" is the remark identifier and "DIR" is the direction from the station. For example, "VIRGA" or "VIRGA SW".

 


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Test Yourself

Challenge yourself with these two long METARs that provide a lot of information. Here are two lengthy METARs filled with various details.


  1. PHNL 291953Z 07010G22KT 7SM +RA SCT025 BKN035 27/22 A3016 RMK AO2 RAB50 SLP212 T02670217 PNO VISNO RWY04R $


2. KOKC 011955Z AUTO 22015G25KT 180V250 3/4SM R17L/2600FT +TSRA BR OVC010CB 18/16 A2992 RMK AO2 TSB25 TS OHD MOV E SLP132

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Final thoughts

Understanding METAR is crucial for anyone interested in aviation. These reports provide vital weather information, helping pilots make informed decisions. By learning how to read and decode METAR, you gain valuable skills that enhance safety and efficiency in flying. Remember, staying updated on weather conditions can make all the difference. Take the time to practice reading METAR codes and improve your aviation knowledge today.




 


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