METAR

METAR
Name	METAR
Type	Aviation weather report
Acronym	METAR
Issued by	Federal Aviation Administration; World Meteorological Organization
First issued	1940s
Frequency	Hourly (routine) / Special as needed
Format	Plain-text encoded observation

METAR

METAR is an international routine aviation surface weather observation code used by airlines, Nav Canada, Federal Aviation Administration, International Civil Aviation Organization, and national meteorological services such as Met Éireann, Météo-France, and the Japan Meteorological Agency. It conveys current conditions including wind, visibility, weather phenomena, sky description, temperature, dew point, and altimeter settings for airports like Heathrow Airport, Hartsfield–Jackson Atlanta International Airport, and Changi Airport. Pilots, air traffic controllers at facilities such as Federal Aviation Administration Air Traffic Control Centers and Eurocontrol planners, dispatchers at Delta Air Lines, and meteorologists at organizations like the National Weather Service rely on METAR to support safe flight operations and strategic planning.

Overview

METAR evolved from observation practices established by agencies including the Royal Air Force, the United States Army Air Corps, and early civil services after World War II to standardize reporting for commercial hubs such as LaGuardia Airport and Charles de Gaulle Airport. The code is maintained through standards set by the International Civil Aviation Organization and recommended practices from the World Meteorological Organization, aligning with protocols used by entities like International Air Transport Association and national services such as the Bureau of Meteorology (Australia). Routine METARs are typically issued hourly, with special reports—known by some operators like Lufthansa and British Airways—issued when significant changes occur. METAR complements terminal forecasts like those produced by National Oceanic and Atmospheric Administration centers and is distinct from trend forecasts used in aerodrome advisories issued by authorities including Nav Canada.

Format and Code Elements

A standard METAR string uses alphanumeric groups defined by the International Civil Aviation Organization Annexes and WMO documents and contains identifiers familiar to users of airports such as Sydney Airport, Dubai International Airport, and Frankfurt Airport. Elements include the station identifier (e.g., codes from ICAO), date-time group synchronized with Coordinated Universal Time, wind group reporting speed and gusts with directions relevant to runways at Los Angeles International Airport or Tokyo Haneda Airport. Visibility follows regional conventions used by Transport Canada and the European Aviation Safety Agency, while present weather codes reference phenomena catalogued by the World Meteorological Organization and used by services like Météo-France and the Deutscher Wetterdienst. Sky condition layers use cloud amount abbreviations aligned with manuals from ICAO and measurement practices of national services such as Servicio Meteorológico Nacional (Argentina). Temperature, dew point, and altimeter (pressure) follow units and encodings consistent with guidance from the International Civil Aviation Organization and calibration procedures used by observatories like the CSIRO.

Reporting Procedures and Issuance

METAR issuance protocols are carried out by meteorological observers at aerodrome stations operated by authorities such as Airservices Australia, Met Office (United Kingdom), and Servicio Meteorológico Nacional (Mexico), or by automated systems managed by agencies like the National Oceanic and Atmospheric Administration. Observers and automated systems follow reporting triggers used by carriers such as United Airlines and regulators like the Federal Aviation Administration to determine when a special report (SPECI) is necessary, for phenomena tracked by organizations including the European Organisation for the Safety of Air Navigation. Dissemination uses networks such as the Global Telecommunications System of the World Meteorological Organization, Aeronautical Fixed Telecommunication Network used by ICAO, and national data feeds to airports, airline operations centers, and flight planning services like Jeppesen. Quality assurance and coordination may involve national aviation authorities such as Transport Canada Civil Aviation and regional bodies like Eurocontrol.

Interpretation and Use in Aviation

Flight crews at airlines including American Airlines and Air France interpret METAR for preflight and in-flight decision-making, integrating METAR with forecasts from National Weather Service centers, NOTAMs issued by Federal Aviation Administration, and traffic flow information from Federal Aviation Administration Air Traffic Control Centers. Air traffic controllers at facilities like New York TRACON and Heathrow Tower use METAR for separation minima, approach briefings, and runway selection decisions; dispatchers at carriers and general aviation pilots incorporate METAR into fuel planning and alternate selection guidelines referenced in operating manuals from authorities such as the European Union Aviation Safety Agency. Training organizations such as the International Air Transport Association and flight schools affiliated with universities like Embry–Riddle Aeronautical University teach METAR decoding alongside instrument procedures used at airports such as Gatwick Airport.

International Standards and Variants

While the core coding is standardized by ICAO and harmonized with WMO manuals, regional variants reflect practices used by national services like Japan Meteorological Agency, Servicio Meteorológico Nacional (Argentina), and Met Office that influence presentation and local conventions employed by airports including Beijing Capital International Airport and Indira Gandhi International Airport. Some countries incorporate additional groups or localized remarks for operations by airlines such as Qatar Airways or Emirates, and specialized products exist for military aerodromes administered by organizations like the United States Air Force and the Royal Australian Air Force. Aviation data aggregators such as FlightAware and SkyVector redistribute METAR alongside TAFs and SIGMETs from providers including National Oceanic and Atmospheric Administration.

Automation and Quality Control

Automated Weather Observing Systems (AWOS) and Automated Surface Observing Systems (ASOS) used by agencies like the National Weather Service and Environment and Climate Change Canada generate METAR-compliant messages, supplemented by human oversight from meteorological services such as Met Éireann and Météo-France. Calibration and verification follow standards and quality control frameworks developed by the World Meteorological Organization and audited by national authorities such as Transport Canada and the Federal Aviation Administration. Data fusion with radar from NEXRAD, satellite feeds from EUMETSAT and NOAA satellites, and surface networks from research institutions like Scripps Institution of Oceanography support anomaly detection, while organizations like Eurocontrol and ICAO coordinate international interoperability and updates.

Category:Aviation weather