Airmen use METAR reports to gain essential knowledge about flight conditions. While a report may look like a series of random numbers to a casual observer, each report contains a large amount of data. These reports are not difficult to decode after knowing what to look for. Once you receive a report from an airport or meteorological center, read the first series to determine the origin of the data. The rest of the report will contain information on visibility, weather and other conditions of all kinds. If you need help, find a chart that explains common abbreviations to understand the type of weather you will deal with when on the track.
Part 1 of 3: Finding the Type and Source of the Report
Step 1. Get a METAR report from an airport aviation center
These reports are usually free and available even when you are not operating an aircraft. Check with your country's government aviation office or the national weather service online. For example, the US Aviation Center for Meteorology offers reports. You can access them here.
If you want to request a report from a weather center, select a location. You can also choose a time period if you want to access a previous report
Step 2. Identify the type of report using the initial letters of the code
If you are looking at a METAR report, you will see that it says so at the beginning. There are also other types of reports, each of which conveys different information. Distinguish between these types of reports to find the weather details you need.
- METAR reports are routine reports that are done every hour. A new METAR report is issued at the end of each hour.
- SPECI indicates an unscheduled special report. SPECI reports are often issued for special conditions (for example, low visibility and thunderstorms).
- TAF stands for "terminal aerodrome forecast", or a forecast of the weather that will occur at an airport. TAFs are similar to METARs but are not as common and are used to provide a forecast for a general area.
Step 3. Look at the station identifier after the report type
The identification tag will be similar to KAFF. The K represents a location in the US and the subsequent letters indicate the station where the report came from. Each country and station has its own identification code given to it by the World Meteorological Organization.
- For example, KAFF represents the Air Force Academy in Colorado.
- EGLL is the code for London Heathrow International Airport. E represents the United Kingdom, while GLL represents Heathrow Airport.
- RJAA represents Narita International Airport.
Step 4. Read the numbers below to find the date and time of the report
Look for a series of 6 numbers followed by a Z (for example, 212355Z). The first pair of numbers represents the day of the month and the rest of the code represents Zulu time, also known as Coordinated Universal Time or Greenwich Mean Time. Note that the report does not include information about the month or year in which it was issued.
For example, in 212355Z, 21 tells you that the report arrived on the 21st of the month. It happened at 2355Z Zulu, which would be 1755 or 11:55 a. m. in Colorado Springs
Step 5. Find a short phrase that explains how the report was modified
In the example, the modifier is indicated by COR. If there is, the modifier information is always listed after the date and time. You can distinguish it from the rest of the report by its short length. It also doesn't have any numbers unlike the codes that come before and after.
- AUTO means that the report came from an automated station.
- COR indicates that someone corrected the initial report. A manual observer changed something where the automated station missed.
- You will not see a modifier for reports that a person has issued. If there is no one on duty at the station, you may start to see automated reports.
Part 2 of 3: Determine Wind and Visibility Factors
Step 1. Look at the first 3 digits of the code below to find the direction of the wind
The following code, which is a combination of letters and numbers, is related to the wind. The direction of the wind is shown according to true north. True north refers to the direction of the Earth's axis rather than the magnetic north seen when looking at a compass. You can find true north with maps or with a compass.
- In the VRB05KT code, VRB represents the wind direction. VRB means that the direction of time varies.
- Also, the first letters of the code could be something like 120. Imagine a compass with 0 degrees at the top and 180 at the bottom. 120 means that the wind blows from the southeast.
Step 2. Find the speed using the remaining digits in the wind code
There are always 2 or 3 numbers after the wind direction that indicate the speed. The speed is in knots or KT, for its abbreviation in English. You may also see some other letters from time to time that describe how hard the wind is blowing.
- In the VRB05KT code, 05KT means that the wind is blowing at a speed of 5 knots.
- You may see the letter G in the middle of the wind report. For example, G26KT represents wind gusts blowing at 26 knots.
- The letter V tells you that a strong wind blowing at more than 6 knots has a variable direction. For example, you might see 180V260. The wind changes direction between 180 and 260 degrees.
Step 3. Review the wind visibility short code to determine air quality
The wind visibility code consists of a short series of numbers that are usually accompanied by a unit of measure. In the US, wind visibility is typically measured in statutory miles. For reports outside of the US, keep in mind that visibility will be in meters.
- A visibility of 15SM means you can see it for about 15 miles (24 km). Also, visibility can be shown as a fraction. If it shows as 1 1 / 2SM, it means visibility is 1 1/2 miles (2.4 km).
- Visibility measured in meters can be listed as 1400 or something similar. The unit of measurement will not appear but you will be able to know that it is in meters, since the measurements in miles do not usually exceed 30.
Step 4. Read series beginning with R to find visibility on the track
A series of letters and numbers like R36L / 2400FT tells you everything you need to know about the track. Information about the runway does not appear in all reports. If you don't see it after the air visibility code, there will be clear ground conditions. Track visibility will tell you how far you can see from the track.
- The first set of numbers indicates which track the report covers. R36 means runway 36. In areas where there are parallel runways, there is a marker like L, which refers to the left runway.
- The second number explains the distance of visibility. In a code that says / 2400FT, the visibility will be 2400 feet (730 m).
Part 3 of 3: Finding Cloud and Weather Information
Step 1. View the current weather conditions if they appear in the report
The codes that come after the wind information explain the significant weather conditions in the area. This can include precipitation, weather intensity, and other factors that have an effect on navigation. Since there are many different signs, consider looking for a chart to interpret them. For example, try the chart here.
|- Light||ME Come down||DZ Drizzle||BR Fog||PO Swirls of dust or sand|
|Moderate (no qualifier)||BC Banks||RA Rain||FG Fog||SQ Turbonated|
|+ Heavy||DR Floating low||YN Snow||FU Smoke||FC Funnel cloud|
|VC Nearby||BL Blowing||SG Snow grains||DU Dust||+ FC Tornado or waterspout|
|SH Showers||IC Ice crystals||SA Sand||H. H Sandstorm|
|TS Electric storm||PL Ice pellets||HZ Mist||DS Dust storm|
|FZ Frozen||GR Hail||PY Spray|
|PR Partial||GS Small hail or snow pellets||GOES Volcanic ash|
|UP Unknown precipitation *|
- For example, you might see -SHRA, which represents light rain.
- The code + TSRA stands for thunderstorms with heavy rain.
Step 2. Use the initial 3 letters of the 6-digit codes to determine the cloud cover
The codes for sky conditions start with 3 letters and end with 3 numbers. The letters tell you how much sky is covered by clouds. In a METAR report, there may be more than one code that describes the different cloud groups, and therefore you should be sure to read the entire report. For example, the report could include FEW040 SCT060 SCT075 SCT090 BKN220.
- SKC is the clear sky code for reports that are generated manually. Automated reports use CLR for elevations below 12,000 ft (3700 m).
- FEW means that there are not many clouds to worry about. Clouds cover 1/8 to 2/8 of the sky.
- SCT indicates scattered clouds, which means that 3/8 to 4/8 of the sky is covered.
- BKN means very cloudy. In these conditions, between 5/8 and 7/8 of the sky will be covered.
- The days covered come with the OVC code. If you see this code, the sky will be completely covered in clouds.
Step 3. Read the numbers below to determine how high the clouds are
The numbers measure the height of the cloud base. This information is contained in hundreds of feet above the ground. If the clouds appear to continue indefinitely, you will notice the letters VV to refer to vertical visibility. You may also see letters at the end of your code that describe special types of clouds.
- For example, BKN220 indicates that the clouds are at 22,000 feet (6700 m). All you have to do is add a pair of 0s to the end of the code to determine the height of the clouds.
- You might also see something like BKN220TCU. TCU refers to a cumulus congestus.
- CB refers to cumulonimbus clouds. These are usually present during storms.
- ACC is an Altocumulus castellanus.
Step 4. View the temperature and dew point marked by a combined number
The numbers for temperature and dew point are separated by a slash. The first indicates the temperature in degrees Celsius and the number after the bar indicates the dew point in Celsius. For example, you might see 15 / M01 in a report.
- In 15 / M01, the temperature is 15 ° C (59 ° F).
- The M before the dew point stands for "minus." A dew point listed as M01 corresponds to -01.
Step 5. Check the altimeter settings for the code that starts with A
The A represents the altimeter and therefore you can always recognize this code that appears after the temperature. The code describes the atmospheric pressure in the area. It will appear either as inches of mercury or as hectopascals. Pilots use this information to ensure that the aircraft's altimeter shows the correct altitude.
- An example of an altimeter setting is A2957, which corresponds to 29.57 inches of mercury, or 29.57 "Hg.
- In general, the altimeter settings in the reports are listed in inches of mercury. Reports outside the US may occasionally use a code such as Q1030, or 1030 hectopascals.
Step 6. Review the comments to find other information that has been added to the report, if applicable
The comment section is for anything else the informant thinks you should know. A METAR report could have very few or many additional comments. These comments can include information about when a thunderstorm started or ended, the type of station issuing the report, air pressure, or any other information. Since so many different comments can be added, be sure to check out a guide like this one.
- For example, ACSL stands for stationary altocumulus lenticular clouds. Then, DSNT indicates that the clouds are distant, more than 16 km (10 miles). The code SE-S indicates that they are to the south-southeast.
- The code SLP960 indicates the pressure at sea level in tenths of a millibar or hectopascals.
- The code SHRA DSNT N-E-SE AND DSNT NW indicates moderate rainfall in the distant north to the east to the southeast and the distant northwest.
- General numbers like 60001 55000 often represent automated maintenance data. You don't need to bother trying to figure them out.
- LAST COR stands for "last correction". The number 43 indicates that the correction was made at a certain time 43 minutes.
- Try to access some local airport reports for practice. Access the METAR and then check it with the conditions you observe outside.
- Because the METAR system is used all over the world, you will be able to read a report from another country without much difficulty.
- The best way to read a METAR report is to take one piece of information at a time. The codes always come in the same general order and don't look the same, so you can determine which part is which by deciphering them one by one.