How to Read and Interpret Aviation Weather Reports

Aviation weather reports are essential for pilots, flight dispatchers, and air traffic controllers to ensure safe and efficient flight operations. Two critical types of weather reports used in aviation are METAR (Meteorological Aerodrome Report) and TAF (Terminal Aerodrome Forecast). Understanding these reports enables aviation professionals to make informed decisions about flight planning, route selection, and overall safety.

In this guide, we will break down METAR and TAF reports; explain their formats and how to interpret them effectively.

UNDERSTANDING METAR REPORTS

What is a METAR Report? – METAR reports provide real-time weather observations at specific airports and are issued hourly or more frequently when significant weather changes occur. These reports include essential meteorological information such as wind speed, temperature, visibility, cloud cover, and precipitation.

METAR Format Breakdown

A standard METAR report follows a structured format. Let’s analyze an example:

METAR    FAOR    181751Z    25010KT    10SM    SHRA    FEW030    SCT050    BKN100    25/18    A2992    RMK AO2 SLP134

Let’s break it down:

1. METAR – This weather report is a METAR type of report which is a routine hourly weather report. However, a SPECI report can be issued when there’s a significant change in weather like if visibility drops below or improves beyond certain thresholds, cloud ceiling (lowest broken or overcast layer) rises above or falls below critical levels, occurrence or cessation of thunderstorms, precipitation (rain, snow, hail), or other factors affecting flight safety. SPECI follows the same format as a METAR, but it is an unscheduled report which means it can come up at any time.
2. NEXT is the station identifier which is a four-letter ICAO airport code. FAOR is the ICAO code for OR Tambo International Airport, Johannesburg. Therefore, the following weather information to OR Tambo International Airport, Johannesburg.
3. 181751Z – This term describes the date and time of report. (181751Z = 18th day of the month at 17:51Z). The alphabet “Z” means that the time of weather report is in Zulu or Greenwich Mean Time.
4. 25010KT – Wind direction and speed given in degrees and speed in knots. From the given METAR; 25010KT means the wind is blowing from 250º true north at a speed of 10 knots.

Gust is denoted by “G” and it is reported on the same section of wind direction/speed. (e.g., 25010G20KT = Wind from 250º at 10 knots, gusting at 20 knots).

5. 10SM – Next is Visibility, and it is reported in statute miles (10SM = 10 statute miles visibility).
6. SHRA – This is the weather phenomena recorded at the time of report. SHRA is a code for moderate rain showers.

Common codes include:

RA (Rain),  SN (Snow),  FG (Fog),  TS (Thunderstorm),  BR (Mist), etc.

" - " denotes light, and "+" denotes heavy (e.g., -RA = Light rain, +SN = Heavy snow).

7. FEW030 SCT050 BKN100 – This section explains the sky condition. It includes cloud cover and height of cloud above ground level.

Cloud cover is reported using: FEW (Few clouds, 1-2 oktas),

SCT (Scattered clouds, 3 - 4 oktas)

BKN (Broken clouds, 5 - 7 oktas)

OVC (Overcast, 8 oktas)

CLR (Clear skies below 12,000 ft for U.S. METARs)

• From the given METAR report: FEW030 SCT050 BKN100

FEW030 – There are Few clouds at 3,000 feet above ground level.

SCT050 – You will find Scattered clouds at 5,000 feet.

BKN100 – Broken cloud layer will be seen at 10,000 feet.

8. 25/18 – This is the temperature and dew point at the time of METAR report, expressed in degree Celsius.

Temperature 25°C and dew point 18°C.

It’s good to note that the dew point temperature is the temperature at which moisture starts to condense based on current humidity.

9. A2992 – Altimeter setting reported in inches of mercury. (29.92 inches of mercury).
10. RMK AO2 SLP134 – Additional remarks such as lightning, wind shifts, or pressure tendencies are reported here.

• From the given METAR report – AO2 SLP134

AO2: The station has a precipitation discriminator.

SLP134: The sea-level pressure is 1013.4 hPa, which is close to the standard atmospheric pressure of 1013.25 hPa at sea level.

UNDERSTANDING TAF REPORTS

A TAF (Terminal Aerodrome Forecast) is a weather forecast for an airport, issued four times a day, and provides expected weather conditions for a 24- or 30-hour period. This report is crucial for flight planning as it predicts weather changes over time.

Here’s an example of a TAF report:

TAF    DNMM    181730Z    1818/1924    20012KT    P6SM    SCT040    BKN080

FM190000   22010KT   P6SM   OVC100

TEMPO   1902/1906   5SM -RA BR

PROB30   1910/1914   2SM   TSRA OVC030CB

Breaking it Down:

1. TAF – This is a TAF report.

2. DNMM – This TAF report belongs to Murtala Muhammed International Airport Lagos, Nigeria.

3. 181730Z – Date and Time issued. (18th day of the month at 17:30 UTC).

4. 1818/1924 – This is the validity period of the given TAF report; expressed as DDHH/DDHH (1818/1924 means valid from 18th day of the month at 1800 UTC and terminates on 19th at 2400 UTC).

5. 20012KT   P6SM   SCT040   BKN080 – This term describes the wind direction and speed, visibility, cloud cover/height above ground level. From the given TAF report, the wind is from 200° with a speed of 12 knots; visibility is greater than 6 statute miles (P6SM – Plus 6 Statute Miles), and there are scattered clouds at 4,000 feet, broken clouds at 8,000 feet.

6. FM190000 – “From” time marker indicating a weather change from 00:00 UTC on the 19th.

FM190000   22010KT   P6SM   OVC100 - From this given date and time (19th/0000 UTC), the wind will come from 220º at a speed of 10 knots, visibility is still greater than 6 statute miles, and overcast cloud at 10,000 feet.

TEMPO   1902/1906   5SM   -RA   BR – (TEMPO = Temporary). Between 0200 and 0600 UTC on the 19th, the following temporary condition is forecasted: visibility reduced to 5 statute miles due to light rain and mist. ( “ - “ = light,  RA = rain,  BR = mist).

PROB30  1910/1914  2SM  TSRA  OVC030CB – (PROB = Probability). Still on the 19th, between the hours of 1000 and 1400 UTC, there is a 30% probability of thunderstorms with heavy rain and overcast cumulonimbus clouds at 3,000 feet.

How to Apply METAR & TAF Knowledge in Flight Planning

Understanding these reports allow pilots to:

Determine Weather Suitability: Assess if weather conditions are safe for departure, en route, and arrival phases.

Plan Alternative Routes: Identify alternative airports in case of unexpected weather deterioration.

Manage Fuel Planning: Adjust fuel calculations based on expected headwinds, turbulence, or alternate airport needs.

Enhance Passenger Safety & Comfort: Predict and mitigate turbulence, strong winds, or thunderstorms.

Interpreting aviation weather reports is a critical skill for every aviation professional. Whether you are a student pilot, a flight dispatcher, or an aviation enthusiast, mastering METAR & TAF reports enhances your ability to make informed flight decisions and improve overall safety.

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