METAR and TAF Decoding for Pilots

Before every flight, sport pilots must build a clear mental picture of both current and forecast weather conditions. The two workhorses of aviation weather reporting are the METAR (Meteorological Aerodrome Report) and the TAF (Terminal Aerodrome Forecast). METARs capture observed surface weather conditions at a specific airport, while TAFs provide forecasts for a 24- to 30-hour window. Together, they anchor the preflight weather briefing described in the Pilot's Handbook of Aeronautical Knowledge (PHAK, FAA-H-8083-25) and the Aviation Weather handbook (FAA-H-8083-28). Understanding how to decode these products accurately is not optional — it is a direct safety skill that keeps VFR pilots on the right side of the weather.

What Is a METAR?

A METAR is an observation of actual conditions recorded at a specific airport or weather station. Routine METARs are issued once per hour, typically at 55 minutes past the hour so they are ready by the top of the hour. When conditions change significantly between routine observations — for example, when visibility drops below three statute miles or a thunderstorm moves in — an unscheduled SPECI (special observation) is issued. Both types use the same coded format.

The United States uses statute miles for visibility and knots for wind in METARs, which aligns with domestic flight operations. Heights are always in feet AGL (above ground level) at the reporting station — a critical detail that will appear on the Sport Pilot knowledge test.

Reading a METAR Group by Group

Consider this sample METAR: METAR KTPA 151955Z 18012G22KT 7SM -SHRA BKN035 OVC080 26/21 A2987 RMK AO2 RAB1932. Each group appears in a fixed sequence:

• Report type: METAR (routine) or SPECI (special). This tells you whether conditions triggered an unscheduled update.
• Station identifier: Four-letter ICAO code. U.S. airports begin with K; Alaskan stations begin with PA; Hawaiian stations with PH.
• Date and time: Six digits followed by Z for Zulu (UTC). 151955Z means the 15th day at 1955 UTC. All aviation weather is reported in UTC to eliminate confusion across time zones.
• Wind: Three-digit true direction the wind is blowing from, followed by speed in knots. 18012G22KT means wind from 180° (due south) at 12 knots, gusting to 22 knots. VRB replaces the direction when winds are light and variable (generally below 6 knots). 00000KT means calm.
• Visibility: In statute miles in the U.S. 7SM means seven statute miles. Values below one mile are given as fractions such as 1/4SM. The symbol M before a fraction (e.g., M1/4SM) means less than that value.
• Weather phenomena: Two-letter codes preceded by intensity qualifiers. A minus sign (-) means light; no sign means moderate; a plus sign (+) means heavy. -SHRA means light rain showers. Common codes include RA (rain), SN (snow), TS (thunderstorm), BR (mist, visibility 5/8 to 6 SM), FG (fog, visibility below 5/8 SM), HZ (haze), and GR (hail). Thunderstorm (TS) always takes priority and is listed first when present.
• Sky condition: Cloud coverage abbreviations paired with height in hundreds of feet AGL. FEW = 1–2 eighths coverage; SCT (scattered) = 3–4 eighths; BKN (broken) = 5–7 eighths; OVC (overcast) = 8 eighths. SKC (sky clear) is used at manual stations; CLR is used by automated stations and means no clouds below 12,000 feet. VV (vertical visibility) replaces cloud groups when the sky is obscured; VV008 means vertical visibility of 800 feet into an obscuration. Layers are listed lowest to highest. BKN035 means a broken layer at 3,500 feet AGL — this constitutes a ceiling.
• Temperature and dew point: Celsius values separated by a slash. 26/21 means temperature 26°C, dew point 21°C. Negative values use M as a minus sign: M04/M08 means −4°C and −8°C. A small spread between temperature and dew point signals high relative humidity and potential for fog or low clouds.
• Altimeter setting: The letter A followed by four digits in inches of mercury (to hundredths). A2987 means 29.87 in. Hg. This value must be set in your altimeter's Kollsman window to receive an accurate altitude reading.
• Remarks (RMK): Free-text additions. AO2 identifies an automated station with a precipitation discriminator (can distinguish rain from snow). RAB1932 means rain began at 1932 UTC. Sea-level pressure, significant weather events, and sensor notes also appear here.

What Is a TAF?

A TAF is a meteorologist-issued forecast for the airspace within approximately five statute miles of a specific airport. TAFs are issued four times daily (0000Z, 0600Z, 1200Z, and 1800Z). Most U.S. TAFs cover a 24-hour period, though a 30-hour TAF is standard at major hubs and terminals. TAFs use the same weather codes as METARs but add special change group indicators that describe how conditions will evolve over time.

TAF Change Groups Explained

The three change indicators are among the most tested TAF elements on FAA knowledge tests:

• FM (From): An abrupt, complete change expected at a specific time. Everything after FM1400, for example, replaces the previous forecast starting at 1400Z. There is no gradual transition — think of it as flipping a switch.
• TEMPO (Temporary): Fluctuations expected to last less than one hour at a time and to occur for less than half of the TEMPO period. TEMPO conditions are brief but real. If a TAF shows TEMPO TSRA, isolated thunderstorms with rain could appear within that window even if most of the period remains clear.
• BECMG (Becoming): A gradual change expected to complete within the two-hour window specified. BECMG 1416 BKN010 means the ceiling will gradually lower to a broken layer at 1,000 feet AGL, with the change completing between 1400Z and 1600Z.

Why METARs and TAFs Matter for Sport Pilots

Sport pilots operating under 14 CFR Part 61 must comply with VFR weather minimums defined in 14 CFR 91.155. In Class G airspace at or below 1,200 feet AGL during the day, the minimums are 1 statute mile visibility and clear of clouds; at night, Class G minimums increase to 3 statute miles visibility, 500 feet below clouds, 1,000 feet above clouds, and 2,000 feet horizontally from clouds. In Class E airspace at and above 1,200 feet AGL, the requirement is 3 statute miles visibility, 500 feet below clouds, 1,000 feet above clouds, and 2,000 feet horizontally from clouds. A METAR showing a ceiling of 800 feet broken immediately tells you that Class D and Class E surface airspace — which require at least a 1,000-foot ceiling — are off-limits without a special VFR clearance, which sport pilots may not request under instrument conditions.

A TAF reading TEMPO TSRA during your planned departure window is a hard stop. The Aviation Weather handbook (FAA-H-8083-28) emphasizes that thunderstorms are among the most hazardous phenomena for light aircraft, and even proximity to a cell can produce severe turbulence, wind shear, and hail. Identifying this risk in a TAF before departure — not after takeoff — is exactly what preflight weather analysis is designed to accomplish.

Key Numbers and Rules

• METARs are issued at least once per hour; SPECIs are unscheduled updates triggered by significant condition changes.
• Cloud heights in both METARs and TAFs are always in feet AGL at the reporting station, never MSL.
• Wind direction is always reported in degrees true and indicates where the wind is blowing from.
• Temperature and dew point are in degrees Celsius; M preceding a value means negative (below freezing).
• The altimeter setting in a U.S. METAR uses the letter A and is expressed in inches of mercury to hundredths.
• TAFs cover approximately five statute miles around the forecast airport; conditions even a few miles away may differ.

Common Test Traps

• Ceiling vs. sky cover: Only BKN, OVC, and VV layers constitute a ceiling. FEW and SCT layers do not, even if they are at low altitudes.
• TEMPO is not guaranteed clear: Because TEMPO fluctuations can occur during the stated period, you cannot assume the period will be free of those conditions.
• Statute miles vs. nautical miles: METAR visibility is in statute miles. Do not confuse this with nautical miles used for distance in navigation.
• FM replaces everything: After an FM group, none of the earlier forecast conditions carry forward. New wind, visibility, sky conditions, and weather all apply.
• M before a temperature means below zero: M02 is −2°C, which is below freezing — relevant when evaluating structural icing risk for any flight near precipitation.
• AO1 vs. AO2: An AO1 automated station lacks a precipitation discriminator and cannot distinguish the type of precipitation; AO2 stations can. This affects how much you trust the weather phenomena group in the remarks.

Memory aid

For the METAR element sequence, many instructors use the phrase "Two Dogs Will Vomit Weather Stuff, Then Arrive Running" — Type, station iDentifier, Date/time, Wind, Visibility, Weather, Sky condition, Temperature/dew point, Altimeter, Remarks. The sequence is always the same, so even a few practice decodings will make it automatic.