METAR and TAF for drone pilots: how to read them for the Part 107 test

The Remote Pilot knowledge test expects you to understand two coded weather products: the aviation routine weather report (METAR) and the terminal aerodrome forecast (TAF). Both are listed under Sources of Weather in the Airman Certification Standards.

Many weather apps now add a plain-language translation, but the FAA's Aviation Weather Handbook still says every pilot should be able to decode the raw text in case a decoded version is not available.

Below, each group is explained in order, both products are decoded in full, and the numbers are tied to the Part 107 weather rules.

METAR vs. TAF: an observation and a forecast

A METAR tells you what is happening now. The FAA Remote Pilot Study Guide describes it as an observation of current surface weather reported in a standard international format.

METARs are issued on a regular schedule and are sometimes called hourly reports because they come out near the top of the hour. If the weather changes significantly in between, a special report (SPECI) can be issued at any time.

A TAF tells you what is expected. It is a forecast for a specified time period covering the area within 5 statute miles of the center of the airport's runway complex, and it uses the same weather codes as a METAR.

Most TAFs cover 24 hours, while some major airports get a 30-hour forecast. Scheduled TAFs are issued four times per day, at 0000, 0600, 1200, and 1800Z.

The order of a METAR, group by group

A METAR follows a fixed sequence, so each group always sits in a predictable place. Learn the order and most of the decoding work is done.

Type of report: METAR is the routine report sent at a regular interval; SPECI is a special report that can be issued at any time to update it.
Station identifier: a four-letter ICAO code. In the contiguous U.S. it is K followed by the three-letter identifier, so Seattle (SEA) becomes KSEA.
Date and time: six digits giving the day of the month, then the hour and minutes. The group always ends in Z, meaning Zulu time (UTC), not local time.
Modifier, when present: AUTO means a fully automated report with no human oversight; COR marks a corrected report that replaces an earlier one with an error.
Wind: the first three digits are the direction the wind is coming from, in tens of degrees relative to true north; the next digits are the speed, followed by KT for knots.
Gusts: a G after the speed introduces the peak gust. For example, 27020G35KT is wind from the west at 20 knots with gusts to 35 knots.
Variable wind: at 6 knots or less the direction may be replaced by VRB, as in VRB03KT. If the direction varies by 60° or more at a higher speed, an extra group such as 180V240 shows the two extremes.
Visibility: statute miles, ending in SM, with a space between a whole number and a fraction (1 1/2SM). An M in front means less than, so M1/4SM is less than a quarter mile.
Present weather: intensity first, then a descriptor, then the phenomenon. A minus sign means light, no sign means moderate, and a plus sign means heavy.
Common weather codes include RA for rain, BR for mist, and TS for thunderstorm, which can be combined with rain as TSRA.
Sky condition: an amount (FEW, SCT, BKN, or OVC) followed with no space by the base height in hundreds of feet above ground level, so BKN014 is a broken layer at 1,400 feet.
Cloud amounts are in eighths of the sky: FEW is 1/8 to 2/8, SCT (scattered) 3/8 to 4/8, BKN (broken) 5/8 to 7/8, and OVC (overcast) 8/8.
Ceiling: the lowest layer reported as broken or overcast. If the sky is totally obscured, the vertical visibility (VV) is the ceiling.
Temperature and dewpoint: whole degrees Celsius separated by a slash, with M meaning minus. 04/M02 is a temperature of 4°C and a dewpoint of -2°C.
Altimeter: the letter A and four digits in inches of mercury, without the decimal point, so A2992 is 29.92 inHg.
Remarks: everything after RMK. AO2 identifies an automated station with a precipitation discriminator, and PRESFR means pressure falling rapidly.

A fully decoded example METAR

The report below is a constructed practice example, not a real observation. Each group is decoded in order. All times are UTC (Zulu).

METAR KDSM 141753Z 31012G22KT 280V340 4SM -RA BR BKN014 OVC030 02/M01 A3002 RMK AO2 PRESFR

METAR: a routine, scheduled report rather than a SPECI.
KDSM: the station. The leading K shows an airport in the contiguous United States.
141753Z: the 14th day of the month at 1753 UTC (Zulu), not local time.
31012G22KT: wind from 310° true at 12 knots, gusting to 22 knots.
280V340: the wind direction is varying between 280° and 340°.
4SM: prevailing visibility of 4 statute miles.
-RA BR: light rain and mist.
BKN014 OVC030: broken clouds at 1,400 feet and overcast at 3,000 feet above ground level. The ceiling is 1,400 feet, the lowest broken layer.
02/M01: temperature 2°C, dewpoint minus 1°C.
A3002: altimeter setting 30.02 inches of mercury.
RMK AO2 PRESFR: remarks follow; the station is automated with a precipitation discriminator; pressure is falling rapidly.

Reading a TAF

A TAF opens with the report type: TAF for a routine forecast, TAF AMD for an amended one, or TAF COR for a corrected one. Next come the four-letter station identifier and the issue date and time in UTC.

The valid period follows. In 1512/1612, the forecast runs from the 15th day of the month at 1200 UTC to the 16th at 1200 UTC. An end time of midnight UTC is written as 24.

The forecast body uses METAR-style groups for wind, visibility, weather, and clouds. Visibility greater than 6 statute miles is written P6SM, and cumulonimbus (CB) is the only cloud type forecast.

Change groups split the forecast into time blocks. These are the ones to recognize:

TAF KDSM 141730Z 1418/1518 30012G20KT 5SM -RA BKN015
     TEMPO 1418/1421 3SM -RA BR OVC009
     FM150200 32010KT P6SM SCT035 PROB30 1508/1512 4SM -SHRA

FM (from): prevailing conditions change significantly in less than an hour. FM is followed by a complete new forecast that replaces everything before it.
TEMPO (temporary): fluctuations with more than a 50 percent probability, each lasting one hour or less and together covering less than half of the stated period. Only the elements that change are listed.
PROB30: a 30 percent chance of a thunderstorm or precipitation event during the stated hours. It is the only probability group used in NWS TAFs.
BECMG (becoming): a gradual change over a longer period, usually two hours. The National Weather Service does not use BECMG in its TAFs, but you should still recognize it.

Decoding the example TAF

The TAF above is also a constructed practice example. Read it line by line:

TAF KDSM 141730Z 1418/1518: a routine forecast issued on the 14th at 1730 UTC, valid from the 14th at 1800 UTC to the 15th at 1800 UTC.
30012G20KT 5SM -RA BKN015: at the start, wind 300° at 12 knots gusting to 20, visibility 5 statute miles in light rain, ceiling broken at 1,500 feet. A weather group is required whenever forecast visibility is 6 statute miles or less.
TEMPO 1418/1421 3SM -RA BR OVC009: between 1800 and 2100 UTC on the 14th, brief periods of 3 statute miles in light rain and mist with an overcast ceiling at 900 feet. Wind is not listed, so it stays as forecast.
FM150200 32010KT P6SM SCT035: from 0200 UTC on the 15th, wind 320° at 10 knots, visibility greater than 6 statute miles, scattered clouds at 3,500 feet. No weather group means no significant weather is expected.
PROB30 1508/1512 4SM -SHRA: a 30 percent chance of 4 statute miles in light rain showers between 0800 and 1200 UTC on the 15th.

How METAR and TAF connect to Part 107 weather minimums

Part 107 sets visibility and cloud-clearance limits you can check against these reports. Under §107.51(c), minimum flight visibility, observed from the control station, is 3 statute miles.

Under §107.51(d), the drone must stay at least 500 feet below the cloud and at least 2,000 feet horizontally from it.

Notice the difference in viewpoint. A METAR reports surface visibility at the station, while the rule defines flight visibility as the average slant distance from your control station at which prominent objects can be seen and identified.

Cloud heights in a METAR are above ground level. With the example ceiling of 1,400 feet, staying 500 feet below it leaves about 900 feet, so the general 400-foot AGL altitude limit is the tighter restriction there.

In the example TAF, the TEMPO period forecasts 3 statute miles and an overcast layer at 900 feet. That visibility is exactly at the Part 107 minimum, so any further drop would put the flight below it.

A step-by-step decoding method

Identify the product: METAR, SPECI, TAF, or TAF AMD.
Check the station identifier and the time. Convert Zulu (UTC) to your local time before judging how current the report is.
Read the wind: direction from true north, speed in knots, any G gust value, and any V variability group.
Read the visibility in statute miles and compare it with the 3 statute mile minimum in §107.51(c).
Decode present weather left to right: intensity, descriptor, then phenomenon.
Find the ceiling: the first BKN, OVC, or VV layer. Multiply its three digits by 100 to get feet above ground level.
For a TAF, read the valid period first, then check each FM, TEMPO, and PROB30 line against your planned flight time.

Common mistakes

Reading the time as local time. METAR and TAF times are UTC, marked with a Z.
Treating FEW or SCT as a ceiling. Only a broken or overcast layer, or vertical visibility, is a ceiling.
Dropping the two zeros from cloud heights. BKN008 is a broken layer at 800 feet.
Missing the M in temperatures. 04/M02 means a dewpoint of -2°C, not 2°C.
Assuming a weather code with no sign has no intensity. RA with no sign is moderate rain.
Treating TEMPO like FM. An FM group replaces the whole forecast, while TEMPO lists only the elements that change temporarily.

Frequently asked questions

What does the Z after the time mean?

It means Zulu time, which is Coordinated Universal Time (UTC), not local time. Convert it before comparing a report with your flight.

Is a FEW or SCT layer a ceiling?

No. The ceiling is the lowest layer reported as broken (BKN) or overcast (OVC), or the vertical visibility when the sky is totally obscured.

What visibility do I need to fly under Part 107?

At least 3 statute miles of flight visibility, as observed from the location of the control station (14 CFR 107.51(c)).

How far from clouds must my drone stay?

At least 500 feet below the cloud and 2,000 feet horizontally from it (14 CFR 107.51(d)).

What area does a TAF cover?

A TAF covers the area within 5 statute miles of the center of the airport's runway complex for its valid period.

What is the difference between TAF and TAF AMD?

TAF is the routine forecast. TAF AMD is an amended forecast, issued when the forecaster judges the current one unrepresentative; it replaces the previous TAF immediately.

Sources

Every fact in this guide is taken from these FAA publications. Check the current edition before your test.