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How to Read METAR Aviation Reports (Complete Guide)

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How to Read METAR Aviation Reports (Complete Guide)

One of the skills pilots must learn and excel at is meteorology. It is important to be adept at reading weather reports and forecasts then using them to make informed flight decisions. There are multiple reports to consult, and METARs are one of the primary sources for current weather information. Learning how to read a METAR is a key part of being a safe pilot.

What are METARs?

A METAR, also known as a Meteorological Aerodrome Report or Meteorological Terminal Aviation Routine Weather Report, is a concise report on the current weather conditions at a given location. METARS are issued hourly just before the top of the hour by the Aviation Weather Center. They are valid for 1 hour after issuance.

Pilots can access METARs through the NOAA National Weather Service Aviation Weather Center or by using an aviation app on a tablet, phone, or other digital device. METARs provide a snapshot of the current weather, which is why they are refreshed hourly.

For the most robust data, pilots should consult both the METAR and TAF reports. TAFs, or terminal aerodrome forecasts, provide a forecast of anticipated weather conditions over the upcoming 24 to 30 hours. TAFs are issued 6 times daily at 0000, 0600, 1200, and 1800. Both METARs and TAFs are written using the same codes and terminology, so once you learn to read one, you will know how to read the other as well.

2 Types of METARs

There are 2 types of METAR reports. The standard report that is published every hour is simply called a METAR. If certain dangerous conditions emerge between the issuance of one METAR and the time another METAR is due to be released, an unscheduled version of a METAR called a SPECI for “special” will be issued. A SPECI report can be triggered by such things as frozen precipitation, low clouds, low visibility, or thunderstorms.

11 Parts of a METAR

A METAR contains large amounts of valuable information condensed down into a very concise report format. The report is comprised of blocks of coded data separated by spaces. To read a METAR, you will need to learn the 11 different parts, what information is included in each, how it is formatted, and what codes can be used.

1.      Type of Report

The first block of text indicates the report type. If you are reading a standard METAR report that is released every hour, the text will read “METAR.” An unscheduled special report will say “SPECI.” Remember that if a SPECI report is issued, that means that inclement weather moved in or developed quickly and unexpectedly since the last standard METAR was issued.

2.      Station Identifier

Once you know what type of report you are reading, you need to confirm the location that the report is for. This is accomplished using a station identifier. In the continental United States, the station identifier includes 4 characters. The first character is the country code prefix – “K” for the continental U.S. The last 3 characters are the station’s standard domestic identifier. Canada uses two-character “CU, CW, CY, or CZ” prefixes, and Mexico’s code is an “MM.” Alaska and Hawaii also have two character prefixes, “PA” and “PH” respectively with “P” indicating that they are located in the Pacific.

3.      Date and Time

The date and time of issuance is next. On a standard METAR expect the time to be shortly before the top of the hour. If you see a time that is not close to the top of the hour, this is a clue that you are reading a SPECI not a standard METAR. The date and time are formatted with the first 2 numbers indicating the day of the month and the next 4 numbers relaying the hour and minutes in 24-hour GMT or Zulu time. A “Z” at the end of the block indicates Zulu time.

4.      Modifier

The modifier element after date and time is not essential and may be eliminated. If you do see a modifier code, it will be either “AUTO” or “COR” and will be attached to the end of the date and time block. “AUTO” means that the report you are reading was generated by an automated station rather than a human meteorologist. If a report is auto generated, the type of sensor equipment used to collect the data will be relayed in the remarks section of the METAR. “COR” advises you that a meteorologist corrected the report. No modifier means that a human observer directly created the report or was logged onto the automated system to provide oversight.

5.      Wind Information

The first weather information that you will get to is the wind conditions. Wind condition is a two-part report including both direction and speed grouped together in one text block. The first three digits of the block represent the wind direction or source of the wind based on tens of degrees from true north. If the wind direction is not sustained but is fluctuating, instead of numbers, the report will read “VRB” for variable.

Immediately after the wind direction is the two- or three-digit wind speed in knots followed by “KT” for knots. If wind gusts are present, the sustained speed will be listed first followed by a “G” for gusts and then the highest gust speed.

6.      Visibility, Weather, and Obstructions to Vision

The sixth group of text in the METAR is for visibility. Visibility is communicated in statute miles (SM) and can be relayed in whole numbers or fractions. The number is followed by an “SM” for statute mile. If visibility is less than 7 statute miles, the report will include weather-and-atmosphere/obstruction to vision in addition to visibility information. An “M” in front of the visibility number means “less than.” The maximum visibility listed is 10 SM, so even if the visibility is great than 10 SM, the report will still read 10 SM.

Larger airports will also include the runway visual range (RVR) in this portion of the METAR. RVRs are communicated with the runway identifier followed by a slash and the visibility in feet followed by “FT” for feet.

7.      Present Weather

The weather portion of the METAR is heavy on code use. Codes are used to relay intensity, descriptor, precipitation, and/or obscuration information. For a complete listing of weather codes that can be used for both METARs and TAFs, review the TAF decoder courtesy of the Aviation Weather Center. Memorize the most common and have a list available if you need to look up a more uncommon code.

8.      Sky Condition

The sky condition part tells pilots what level of cloud cover they can expect at different altitudes. You may see as little as one block of text if, for example, skies are completely clear, or many blocks if cloud cover is present and its prevalence varies by altitude.

The major sky conditions codes you will see include:

  • VV – Vertical visibility
  • SKC – Clear (manual report)
  • CLR – Clear (automated report)
  • FEW – Few (1/8 to 1/4 of sky covered)
  • SCT – Scattered (3/8 to 1/2 of sky covered)
  • BKN – Broken (5/8 to 7/8 of sky overed)
  • OVC – Overcast (complete sky coverage)

The altitudes follow the condition code and they are communicated in thousands of feet, so add two zeroes to the number you see to get the actual altitude.

Pay close attention to the end of the sky condition code because any significant and potentially dangerous cloud formations will be annotated there following the altitude code. Codes to watch out for include:

  • TCU – Towering Cumulus
  • CBMAM – Cumulonimbus Mammatus
  • CB – Cumulonimbus or shower/thunderstorm
  • ACC – Altocumulus Castellanus
  • SCSL – Stratocumulus Standing Lenticular
  • ACSL – Altocumulus Standing Lenticular
  • CCSL – Cirrocumulus Standing Lenticular

9.      Temperature and Dew Point

The temperature and dew point block follows sky condition. This data point reads as a fraction with the temperature in degrees Celsius first followed by dew point in degrees Celsius. On very cold days you may see an “M” in front of your temperature number. This stands for “minus” and means temperatures are below 0 degrees Celsius.

10.  Altimeter and Pressure

The barometric pressure data used to calibrate your altimeter is found in this text block. Look for an “A” for altimeter followed by the four-digit barometric pressure reading) in inches of mercury (inHg).

11.  Remarks

The remarks section of a METAR is not always used, but when it is, it is often regarded as the most difficult to translate. Aviation weather apps do not usually auto translate it, and there are so many possible information types and codes that it is nearly impossible to memorize them all. The remarks portion of the report (if applicable) is indicated with a “RMK” followed by the remarks themselves. Remarks provide additional information and details that are important and relevant but that did not fall under any of the standard METARs categories. This can include content like volcanic eruptions, lightning, hailstone sizes, virga, and more.

Head over to Think Aviation for a thorough guide on reading and understanding METAR remarks.

Sample METAR

Now that we have covered all 11 parts of the METAR, it is time to practice reading one. Here is a sample METAR text block:

METAR KLAL 151250Z 11004KT 10SM SCT030 26/24 A3004

1.      Type of Report

METAR – this is a standard METAR report

2.      Station Identifier

KLAL– The K prefix indicates the continental United States, and LAL is the ICAO code for Lakeland Linder International Airport in Lakeland, FL.

3.      Date and Time

151250Z – This report was prepared on the 15th of the month at 1250 Zulu time.

4.      Modifier

This report has no modifier

5.      Wind Information

11004KT – The wind is from one one zero degrees and is sustained at 4 knots. You would read this as “Winds one one zero at 4 knots.”

6.      Visibility

10SM – The visibility is 10 statute miles (or greater, since 10 is the maximum listed visibility).

7.      Present Weather

There is no significant weather present.

8.      Sky Condition

SCT030 – There are scattered clouds at 3,000 feet.

9.      Temperature and Dew Point

26/24 – The temperature is 26 degrees Celsius and the dew point is 24 degrees Celsius.

10.  Altimeter and Pressure

A3004 – The barometric pressure for the altimeter setting is 30.04 inMg.

11.  Remarks

There are no remarks on this report.

Now that you have practiced decoding a basic, straightforward METAR, take a stab at a much more complex and convoluted version courtesy of MzeroA. First watch the video that gives you the METAR to decode, give it a try, and then watch the answer video where Jason walks you through the decoding process. Most METARs you see should not be this complex, but it gives you a good idea of just how much data can be put into one METAR. This METAR also showcases an example of what the remarks section can look like.

Takeaways

METARs are an important meteorological tool that provides pilots with current weather conditions at both their departure and destination airports. METARs are written in a specific format using special codes.

Learning how to read a METAR is not that difficult once you walk through each of the parts. One of the best ways to learn is by doing, and with the Aviation Tutorials Weather Statements 3.0, you don’t have to wait until you are in the air to get some practice. The interactive, multimedia tutorials guide you through the practice of reading METARs, TAFs, and PIREPs. By the time you have completed all thirty-eight learning modules, you will have a strong grasp of the content and be confident in your ability to read all three types of weather statements.

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