AeroWeather Guide: Interpret METARs and TAFs Like a ProUnderstanding METARs and TAFs is essential for safe and efficient flight planning. AeroWeather aggregates and displays these aviation weather reports—METARs (real-time observations) and TAFs (forecasts)—so pilots, dispatchers, and aviation enthusiasts can quickly interpret current and expected conditions. This guide walks through the structure of METARs and TAFs, common abbreviations and codes, how to interpret key elements, practical examples using AeroWeather, and tips to make confident, operationally sound decisions.
What are METARs and TAFs?
- METAR is an aviation routine weather report providing observed conditions at an airport at a specific time (usually issued hourly).
- TAF (Terminal Aerodrome Forecast) is a concise statement of expected meteorological conditions for an airport over a specified period (commonly 24–30 hours).
Both are standardized by ICAO/WMO and used worldwide. AeroWeather pulls these products so you can view them in raw form and decoded formats.
METAR structure — section by section
A typical METAR might look like this: KJFK 021151Z 18012KT 10SM FEW050 ⁄16 A3012 RMK AO2 SLP199
Key components:
- Station identifier: KJFK — ICAO airport code.
- Date/time: 021151Z — day of month (02) and time (1151 Zulu/UTC).
- Wind: 18012KT — wind from 180° at 12 knots.
- Visibility: 10SM — 10 statute miles (US format). Outside the US, meters are used (e.g., 9999 = 10 km or more).
- Cloud cover: FEW050 — few clouds at 5,000 ft. Common cloud codes: SKC/CLR (clear), FEW (1–2 oktas), SCT (3–4), BKN (5–7), OVC (8).
- Temperature/dew point: ⁄16 — temp 28°C, dew point 16°C.
- Altimeter: A3012 — altimeter 30.12 inHg (US). ICAO metric uses QNH (e.g., Q1013 = 1013 hPa).
- Remarks: RMK AO2 SLP199 — additional info (e.g., automated station type, sea-level pressure).
Common METAR abbreviations and modifiers
- Weather intensity/descriptor: – light, no sign = moderate, + heavy, VC = in the vicinity.
- Weather phenomena: RA rain, SN snow, DZ drizzle, FG fog, BR mist, TS thunderstorm, SH shower, GR hail, PL ice pellets. Combinations appear consecutively (e.g., +TSRA = heavy thunderstorm with rain).
- Wind shear: WS or RE for recent phenomena.
- Recent weather: RE indicates occurred within the past hour (e.g., RERA = recent rain).
- Trend groups: BECMG (becoming), TEMPO (temporary), PROB30/40 (probability).
TAF structure — what to look for
A sample TAF: TAF KJFK 021130Z 0212/0318 18012KT P6SM FEW050
FM021800 20010KT P6SM BKN040 TEMPO 0220/0224 3SM -RA BKN020 PROB30 0300/0303 TSRA Key parts:
- Header: TAF KJFK 021130Z 0212/0318 — issued at 1130Z on the 2nd; valid from 0212Z to 0318Z (period start/end).
- Forecast groups: time-tagged blocks (e.g., FM021800 = from 02 at 1800Z onwards change to specified conditions).
- Wind/visibility/clouds follow same coding as METAR.
- TEMPO/PROB/BECMG groups indicate temporary or probable changes over subperiods.
- FM (from) indicates rapid, lasting change at a specified time. Use FM for significant, relatively quick transitions.
Interpreting visibility and ceilings for VFR/IFR decisions
- Visibility: in METARs/TAFs visibility is critical. In the US you’ll often see statute miles (SM); elsewhere you’ll see meters or codes like 9999.
- Ceiling: the lowest broken or overcast layer (BKN/OVC) determines the ceiling.
- Basic operational thresholds:
- VFR: ceiling > 3,000 ft AGL and visibility ≥ 5 SM (US general guidance).
- MVFR: ceiling 1,000–3,000 ft and/or visibility 3–5 SM.
- IFR: ceiling 500–1,000 ft and/or visibility 1–3 SM.
- LIFR: ceiling < 500 ft and/or visibility < 1 SM.
These categories help quick risk assessment but cross-check with regulations, company minima, and approach requirements.
Decoding examples — walk-throughs
Example METAR: EGLL 021150Z 24008KT 9999 SCT025 ⁄12 Q1018 NOSIG
- EGLL = London Heathrow (ICAO).
- 021150Z = 2nd day, 1150Z.
- 24008KT = wind 240° at 8 kt.
- 9999 = visibility 10 km or more.
- SCT025 = scattered clouds at 2,500 ft (AGL).
- ⁄12 = temp 20°C / dew point 12°C.
- Q1018 = altimeter 1018 hPa.
- NOSIG = no significant change expected.
Example TAF: TAF EGLL 021100Z 0212/0312 23008KT 9999 SCT025
FM021800 24010KT 8000 -RA BKN012 TEMPO 0220/0224 3000 SHRA - Expect mostly good conditions, but starting 1800Z winds increase and light rain reduces visibility to 8 km with broken clouds at 1,200 ft; temporary heavier showers could reduce to 3 km.
Practical AeroWeather tips
- Use the decoded view in AeroWeather for faster reading, but verify with raw METAR/TAF when planning critical phases.
- Set airport favorites and wind/ceiling alarms for your minima.
- Pay attention to time stamps (Z) and validity periods—TAFs use UTC always.
- Watch TEMPO/PROB and FM groups for how long and how likely deteriorations are. A short TEMPO to IFR conditions during an approach window is high risk.
- Cross-check METAR recent weather (RE) and remarks (RMK) for sensor limitations or recent convective activity.
Special items pilots often miss
- RVR vs visibility: Runway Visual Range (RVR) may be provided separately and can differ from reported surface visibility—use RVR for runway-specific minima.
- Wind shear and gust notes: gusts (G) and microburst/LLWS mentions in remarks can be critical at low levels.
- Automated station limitations: AO1 lacks precipitation sensor; AO2 has it—check RMK for sensor type.
- Probabilistic groups: PROB30/40 indicate chance; combine with TEMPO duration to judge operational impact.
Quick decoding cheat sheet
- Cloud amounts: SKC/CLR, FEW, SCT, BKN, OVC.
- Visibility: SM (statute miles) or meters (9999 = 10 km+).
- Wind: ddffKT (direction degrees + speed), G for gusts.
- Weather codes: RA, SN, FG, BR, TS, SH, GR, DZ.
- Trends: FM (from), BECMG (becoming), TEMPO (temporary), PROB (probability), NOSIG (no significant change).
Putting it together — a short workflow for flight planning
- Check latest METAR for current conditions and wind.
- Review TAF for expected changes during your operation window; focus on FM/TEMPO/PROB groups.
- Compare ceiling/visibility against your VFR/IFR minima and approach minima.
- Look at trends, recent weather, and remarks for transient hazards (TS, wind shear, precipitation type).
- If uncertain, get an updated briefing from ATC/flight service and consider delaying or diverting if forecasts indicate marginal to below-minima conditions.
Closing note
Mastering METARs and TAFs takes practice. Use AeroWeather’s decoded displays, alarms, and favorite airport lists to build situational awareness quickly. Regularly decode raw messages yourself until the abbreviations become second nature—then interpreting forecasts will feel like reading a weather sentence instead of a puzzle.
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