How to Read METAR Weather Reports

Weather plays a key role in the jobs of aviation personnel. Despite the development of advanced aircraft technology, unfavorable weather conditions can still be a problem which can pose dangers to both human lives and property. This fact is more magnified in the case of drones or UAVs that are much smaller and more easily influenced by winds and rain.

As part of the process of getting a Part 107 drone license, drone pilots are expected to understand weather reports. A standard method of reporting weather conditions is the Meteorological Terminal Aviation Routine Weather Report (METAR) – a highly abbreviated format that contains a lot of information and is not that easy to comprehend for the uninitiated. In this article, we break down METAR reports into their individual elements to help you read and understand them.

What is a METAR report?

To get us started, here is an example of a METAR report:

METAR KCLE 220136Z 31006KT 10SM FEW020 BKN024 OVC049 22/21 A2984 RMK A02 RAE04 P0000 T02220206

It may look like a jumble of random letters and numbers, but it is the most common method of weather reporting that allows for quick transmittal of comprehensive information on prevailing weather conditions. Since METAR reports are highly standardized by the International Civil Aviation Organization (ICAO), they are understood throughout most of the world.

To help understand this METAR report, we highlight and describe each of its elements.

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1. Type of report

METAR KCLE 220136Z COR 31006KT 10SM SHRA FEW020 BKN024 OVC049 15/M01 A2984 RMK A02 RAE04 P0000 T02220206

Although a report identifier is not always present, the absence of this identifier implies that it is a METAR report. METAR reports are regular reports that are released hourly. In extraordinary cases, unscheduled reports are released. These unscheduled and special reports can be identified with the SPECI tag.

2. Station identifier

METAR KCLE 220136Z COR 31006KT 10SM SHRA FEW020 BKN024 OVC049 15/M01 A2984 RMK A02 RAE04 P0000 T02220206

The next element of a METAR report specifies the station that is issuing the report. For stations in the United States, this term can be distinguished with a K prefix. In our example, KCLE refers to the Cleveland Hopkins Airport. There are thousands of stations that issue METARS, and the list of standard identifiers is maintained by the World Meteorological Organization (WMO).

As part of your preparation if you are planning to fly a drone commercially, you need to identify the nearby airports and weather stations and scan for METARs that they are issuing. This way you do not need to remember a lot of station identifiers and screen only for the METARs that are relevant to you.

3. Date and time

METAR KCLE 220136Z COR 31006KT 10SM SHRA FEW020 BKN024 OVC049 15/M01 A2984 RMK A02 RAE04 P0000 T02220206

The third element of the METAR describes the date and time that the report was issued. The first two numbers refer to the day of the month (22) and the next four numbers refer to the time (0136). Take note that the report does not give any indication of the month or the year. The Z suffix of this element means that the time is in Zulu, or in Greenwich Mean Time. Depending on your location, it is best if you get used to converting GMT to your local time.

4. Modifier

METAR KCLE 220136Z COR 31006KT 10SM SHRA FEW020 BKN024 OVC049 15/M01 A2984 RMK A02 RAE04 P0000 T02220206

Though not always present, this element of the METAR indicates if the report was issued by an automate stations (AUTO) or if the report was corrected from an automated report (COR).

5. Wind information

METAR KCLE 220136Z COR 31006KT 10SM SHRA FEW020 BKN024 OVC049 15/M01 A2984 RMK A02 RAE04 P0000 T02220206

The next element of the METAR summarizes the wind conditions. The first three numbers (310) refer to the direction of the source of wind in degrees. In some cases, a variable wind direction can be reported as ‘VRB’.

The numbers after the wind direction refer to the wind speed in knots (06KT = 6 knots). In cases where gusts of wind are being experienced, the highest gust speed is displayed after the wind speed. For example, 31006G12KT refers to a wind speed of 6 knots and gusts that can reach up to 12 knots.

6. Visibility

METAR KCLE 220136Z COR 31006KT 10SM SHRA FEW020 BKN024 OVC049 15/M01 A2984 RMK A02 RAE04 P0000 T02220206

In meteorology, visibility is measured in statute miles (SM). In our example, visibility is limited to 10 statute miles (10SM). It is also possible to report visibility to within a fraction of a statute mile. For instance, 10 1/2SM refers to a visibility of 10.5 statute miles.

7. Present weather

METAR KCLE 220136Z COR 31006KT 10SM SHRA FEW020 BKN024 OVC049 15/M01 A2984 RMK A02 RAE04 P0000 T02220206

This term is not always present but can be used to describe present weather conditions and the presence of obscurations, if any. In our example, SHRA refers to the presence of rainshowers (SH = shower, RA = rain). This term can be even be more specific using the various descriptors and intensity indicators as described below:

8. Sky condition

METAR KCLE 220136Z COR 31006KT 10SM SHRA FEW020 BKN024 OVC049 15/M01 A2984 RMK A02 RAE04 P0000 T02220206

The next block is probably the longest part of any METAR and describes the sky conditions at different altitudes. The prefixes are interpreted as follows:

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 covered)

OVC : overcast (total sky coverage)

The numbers following each prefix refer to the base height of the clouds in these conditions, expressed in hundreds of feet above ground. In our example, there are dew clouds at 2000 feet (FEW020), broken clouds at 2400 feet (BKN024), and overcast conditions at 4900 feet and above (OVC049).

9. Temperature and dew point

METAR KCLE 220136Z COR 31006KT 10SM SHRA FEW020 BKN024 OVC049 15/M01 A2984 RMK A02 RAE04 P0000 T02220206

The next term describes the actual measured temperature and the dew point temperature, both expressed in °C. Simply put, the dew point temperature is the temperature at which moisture in the form start to condense to water.

In our example (15/M01), the temperature is 15 °C and the dew point temperature is -1 °C. The M prefix indicates that the temperature reading is in the negative region.

10. Altimeter and pressure

METAR KCLE 220136Z COR 31006KT 10SM SHRA FEW020 BKN024 OVC049 15/M01 A2984 RMK A02 RAE04 P0000 T02220206

The next term describes the current sea level pressure, expressed in inches of mercury (inHg). This information is used by pilots to check if their altimeters are calibrated correctly and are describing the correct altitude.

In our example, the A2984 term means that the sea pressure is at 29.84 inHg. Although the standard sea level pressure is 29.92 inHg, localized weather conditions and disturbances can incrementally shift this value.

11. Remarks

METAR KCLE 220136Z COR 31006KT 10SM SHRA FEW020 BKN024 OVC049 15/M01 A2984 RMK A02 RAE04 P0000 T02220206

Finally, the last few terms include any remarks that the reporting station deems to be relevant. The whole remarks section is preceded by the ‘RMK’ indicator. This section has highly varied contents and may contain information on the type of stations issuing the report, when a thunderstorm has begun or ended, sea level pressure, information on localized precipitation, hourly temperature and dew point (to a tenth of a degree), any corrections made to the report, and any station maintenance data.

In our example, the remarks section says that the report was issued by an automated station with a precipitation sensor (A02), rain has ended at 4 minutes past the hour (RAE04), there has been no precipitation within the hour (P0000), and that the hourly temperature and dew point temperature is 22.2 °C and 20.6 °C, respectively (T02220206).

The remarks section may be the most difficult part of the METAR to interpret due to the huge variety of information that it can contain. More detailed decoding guides and abbreviation charts for the METAR remarks section can be found in many websites, such as the DixWx Weather Source.

Final thoughts

By analyzing the elements that comprise a METAR report, it is easy to understand how they can be useful to professional drone pilots. The information on the amount of precipitation, wind speed, and cloud coverage can help a drone pilot decide if they should go ahead with a planned flight or not. The prevailing temperature and pressure conditions also influence how much lift a drone’s propellers can generate, which could be especially important for a pilot who uses drones with customizable and heavy payloads.

Thankfully, knowledge on how to interpret METAR reports has been incorporated into the qualifications of a Part 107-licensed drone pilot. It takes a little bit of practice to be comfortable with reading METAR reports, but it is not overly complicated. METAR reports also probably have more information than a drone pilot could ever need, but it is better then going out blind. With the skill to interpret METAR reports, professional drone pilots can perform long flights without surprises.