METAR

For the village in Iran, see Metar, Iran. For the Israeli town, see Meitar.

METAR is a format for reporting weather information. A METAR weather report is predominantly used by pilots in fulfillment of a part of a pre-flight weather briefing, and by meteorologists, who use aggregated METAR information to assist in weather forecasting.

Raw METAR is the most common format in the world for the transmission of observational weather data. It is highly standardized through the International Civil Aviation Organization (ICAO), which allows it to be understood throughout most of the world.

Origin

METARs typically come from airports or permanent weather observation stations. Reports are generated once an hour or half-hour, but if conditions change significantly, a report known as a special (SPECI) may be issued. Some METARs are encoded by automated airport weather stations located at airports, military bases, and other sites. Some locations still use augmented observations, which are recorded by digital sensors, encoded via software, and then reviewed by certified weather observers or forecasters prior to being transmitted. Observations may also be taken by trained observers or forecasters who manually observe and encode their observations prior to transmission.

History

The METAR format was introduced 1 January 1968 internationally and has been modified a number of times since. North American countries continued to use a Surface Aviation Observation (SAO) for current weather conditions until 1 June 1996, when this report was replaced with an approved variant of the METAR agreed upon in a 1989 Geneva agreement. The World Meteorological Organization's (WMO) publication No. 782 "Aerodrome Reports and Forecasts" contains the base METAR code as adopted by the WMO member countries.[1]

Naming

The United States Federal Aviation Administration (FAA) lays down the definition in its publication the Aeronautical Information Manual as aviation routine weather report[2] while the international authority for the code form, the WMO, holds the definition to be aerodrome routine meteorological report. The National Oceanic and Atmospheric Administration (part of the United States Department of Commerce) and the United Kingdom's Met Office both employ the definition used by the FAA. METAR is also known as Meteorological Terminal Aviation Routine Weather Report[3] or Meteorological Aerodrome Report.[4]

Information contained in a METAR

A typical METAR contains data for the temperature, dew point, wind speed and direction, precipitation, cloud cover and heights, visibility, and barometric pressure. A METAR may also contain information on precipitation amounts, lightning, and other information that would be of interest to pilots or meteorologists such as a pilot report or PIREP, colour states and runway visual range (RVR).

In addition, a short period forecast called a TREND may be added at the end of the METAR covering likely changes in weather conditions in the two hours following the observation. These are in the same format as a Terminal Aerodrome Forecast (TAF).

The complement to METARs, reporting forecast weather rather than current weather, are TAFs. METARs and TAFs are used in VOLMET broadcasts.

Regulation

METAR code is regulated by the World Meteorological Organization in consort with the International Civil Aviation Organization. In the United States, the code is given authority (with some U.S. national differences from the WMO/ICAO model) under the Federal Meteorological Handbook No. 1 (FMH-1), which paved the way for the U.S. Air Force Manual 15-111[5] on Surface Weather Observations, being the authoritative document for the U.S. Armed Forces. A very similar code form to the METAR is the SPECI. Both codes are defined at the technical regulation level in WMO Technical Regulation No. 49, Vol II, which is copied over to the WMO Manual No. 306 and to ICAO Annex III.

METAR conventions

Although the general format of METARs is a global standard, the specific fields used within that format vary somewhat between general international usage and usage within North America. Note that there may be minor differences between countries using the international codes as there are between those using the North American conventions. The two examples which follow illustrate the primary differences between the two METAR variations.[6][7]

Example METAR codes

International METAR codes

The following is an example METAR from Burgas Airport in Burgas, Bulgaria. It was taken on 4 February 2005 at 16:00 Coordinated Universal Time (UTC).

METAR LBBG 041600Z 12012MPS 090V150 1400 R04/P1500N R22/P1500U +SN BKN022 OVC050 M04/M07 Q1020 NOSIG 8849//91=

Some locations will report the runway using 3 characters (e.g. 25L)

North American METAR codes

North American METARs deviate from the WMO (who write the code on behalf of ICAO) FM 15-XII code. Details are listed in the FAA's Aeronautical Information Manual (AIM), but the non-compliant elements are mostly based on the use of non-standard units of measurement. This METAR example is from Trenton-Mercer Airport near Trenton, New Jersey, and was taken on 5 December 2003 at 18:53 UTC.

METAR KTTN 051853Z 04011KT 1/2SM VCTS SN FZFG BKN003 OVC010 M02/M02 A3006 RMK AO2 TSB40 SLP176 P0002 T10171017=[9]

Note that what follows are not part of standard observations outside of the United States and can vary significantly.

In Canada, RMK is followed by a description of the cloud layers and opacities, in eighths (oktas). For example, CU5 would indicate a cumulus layer with 5/8 opacity.[12]

Cloud reporting

Cloud coverage is reported by the number of 'oktas' (eighths) of the sky that is occupied by cloud.

This is reported as:[13]

Abbreviation Meaning
SKC "No cloud/Sky clear" used worldwide but in North America is used to indicate a human generated report[14][15]
CLR "No clouds below 12,000 ft (3,700 m) (U.S.) or 25,000 ft (7,600 m) (Canada)", used mainly within North America and indicates a station that is at least partly automated[14][15]
NSC "No (nil) significant cloud", i.e., none below 5,000 ft (1,500 m) and no TCU or CB. Not used in North America.
FEW "Few" = 1–2 oktas
SCT "Scattered" = 3–4 oktas
BKN "Broken" = 5–7 oktas
OVC "Overcast" = 8 oktas, i.e., full cloud coverage
VV Clouds cannot be seen because of fog or heavy precipitation, so vertical visibility is given instead.

Flight categories in the U.S.

METARs can be expressed concisely using so-called aviation flight categories, which indicates what classes of flight can operate at each airport by referring to the visibility and ceiling in each METAR. Four categories are used in the U.S.:[16]

Category Visibility Ceiling
VFR > 5 mi and > 3000 ft AGL
Marginal VFR Between 3 and 5 mi and/or Between 1,000 and 3,000 ft AGL
IFR 1 mi or more but less than 3 mi and/or 500 ft or more but less than 1,000 ft
Low IFR < 1 mi and/or < 500 ft

METAR WX codes

METAR abbreviations used in the WX section. Remarks section will also include began and end times of the weather events.[17]

Codes before remarks will be listed as "-RA" for "light rain". Codes listed after remarks may be listed as "RAB15E25" for "Rain began at 15 minutes after the top of the last hour and ended at 25 minutes after the top of the last hour."

Type Abbreviation Meaning Abbreviation Meaning
Intensity - Light intensity blank Moderate intensity
Intensity + Heavy intensity VC In the vicinity
Descriptor MI Shallow (French: Mince) PR Partial
Descriptor BC Patches (French: Bancs) DR Low drifting
Descriptor BL Blowing SH Showers
Descriptor TS Thunderstorm FZ Freezing
Precipitation RA Rain DZ Drizzle
Precipitation SN Snow SG Snow Grains
Precipitation IC Ice Crystals PL Ice Pellets
Precipitation GR Hail (French: Grêle) GS Small Hail and/or Snow Pellets (French: Grésil)
Precipitation UP Unknown Precipitation
Obscuration FG Fog VA Volcanic Ash
Obscuration BR Mist (French: Brume) HZ Haze
Obscuration DU Widespread Dust FU Smoke (French: Fumée)
Obscuration SA Sand PY Spray
Other SQ Squall PO Dust or Sand Whirls
Other DS Duststorm SS Sandstorm
Other FC Funnel Cloud
Time B Began At Time E Ended At Time
Time 2 digits Minutes of current hour 4 digits Hour/Minutes Zulu Time

U.S. METAR abbreviations

The following METAR abbreviations are used in the United States; some are used worldwide:[6]

METAR and TAF Abbreviations and Acronyms:

Abbreviation Meaning Abbreviation Meaning
$ maintenance check indicator / indicator that visual range data follows; separator between temperature and dew point data.
ACC altocumulus castellanus ACFT MSHP aircraft mishap
ACSL altocumulus standing lenticular cloud ALP airport location point
ALQDS All Quadrants (Official) ALQS All Quadrants (Unofficial)
AO1 automated station without precipitation discriminator AO2 automated station with precipitation discriminator
APCH approach APRNT apparent
APRX approximately ATCT airport traffic control tower
AUTO fully automated report C center (with reference to runway designation)
CA cloud-air lightning CB cumulonimbus cloud
CBMAM cumulonimbus mammatus cloud CC cloud-cloud lightning
CCSL cirrocumulus standing lenticular cloud cd candela
CG cloud-ground lightning CHI cloud-height indicator
CHINO sky condition at secondary location not available CIG ceiling
CONS continuousCOR correction to a previously disseminated observation
DOC Department of CommerceDOD Department of Defense
DOT Department of TransportationDSIPTG dissipating
DSNT distantDVR dispatch visual range
E east, ended, estimated ceiling (SAO)FAA Federal Aviation Administration
FIBI filed but impracticable to transmit FIRST first observation after a break in coverage at manual station
FMH-1 Federal Meteorological Handbook No.1, Surface Weather Observations & Reports (METAR) FMH2 Federal Meteorological Handbook No.2, Surface Synoptic Codes
FROPA frontal passage FROIN Frost On The Indicator
FRQ frequent FT feet
FZRANO freezing rain sensor not available G gust
HLSTO hailstone ICAO International Civil Aviation Organization
INCRG increasing INTMT intermittent
KT KNOTS L left (with reference to runway designation)
LAST last observation before a break in coverage at a manual station LST Local Standard Time
LTG lightning LWR lower
M minus, less than MAX maximum
METAR routine weather report provided at fixed intervals MIN minimum
MOV moved/moving/movement MT mountains
N north N/A not applicable
NCDC National Climatic Data Center NE northeast
NOS National Ocean Survey NOSPECI no SPECI reports are taken at the station
NOTAM Notice to Airmen NW northwest
NWS National Weather Service OCNL occasional
OFCM Office of the Federal Coordinator for Meteorology OHD overhead
OVR overP indicates greater than the highest reportable value
PCPN precipitationPK WND peak wind
PNO precipitation amount not availablePRES Atmospheric pressure
PRESFR pressure falling rapidlyPRESRR pressure rising rapidly
PWINO precipitation identifier sensor not availableR right (with reference to runway designation), runway
RTD Routine Delayed (late) observationRV reportable value
RVR Runway visual rangeRVRNO RVR system values not available
RWY runwayS south
SCSL stratocumulus standing lenticular cloud SE southeast
SFC surface, i.e., ground level) SLP sea-level pressure
SLPNO sea-level pressure not availableSM statute miles
SNINCR snow increasing rapidly SOG Snow on the ground
SPECI an unscheduled report taken when certain criteria have been met STN station
SW southwest TCU towering cumulus
TS thunderstorm TSNO thunderstorm information not available
TWR tower UNKN unknown
UTC Coordinated Universal TimeV variable
VIS visibilityVISNO visibility at secondary location not available
VR visual rangeVRB variable
W west WG/SO Working Group for Surface Observations
WMO World Meteorological Organization WND wind
WS wind shear WSHFT wind shift
Z Zulu, i.e., Coordinated Universal Time

U.S. METAR numeric codes

Additional METAR numeric codes listed after RMK.[17] [18]

Code Description
11234 6 hour maximum temperature. Follows RMK with five digits starting with 1. Second digit is 0 for positive and 1 for negative. The last 3 digits equal the temperature in tenths.

This example value equals -23.4 °C.

20123 6 hour minimum temperature. Follows RMK with five digits starting with 2. Second digit is 0 for positive and 1 for negative. The last 3 digits equal the temperature in tenths.

This example value equals 12.3 °C (54 °F).

4/012 Total snow depth in inches. Follows RMK starting with 4/ and follow by 3 digit number that equals snow depth in inches.

This example value equals 12 inches of snow currently on the ground.

402340123 24-hour maximum and minimum temperature. Follows RMK with nine digits starting with 4. The second and sixth digit equals 0 for positive for 1 for negative. Digits 3–5 equal the maximum temperature in tenths and the digits 7–9 equals the minimum temperature in tenths.

This example value equals 23.4 °C (74 °F) and 12.3 °C (54 °F).

520063 hour pressure tendency. Follows RMK with 5 digits starting with 5. The second digit gives the tendency. In general 0–3 is rising, 4 is steady and 5–8 is falling. The last 3 digits give the pressure change in tenths millibars in the last 3 hours.

This example indicates a rising tendency of 0.6 millibars.[19]

601233 or 6 hour precipitation amount. Follows RMK with 5 digits starting with 6. The last 4 digits are the inches of rain in hundredths. If used for the observation nearest to 00UTC, 06UTC, 12UTC, or 18UTC, it represents a 6-hour precipitation amount. If used in the observation nearest to 03UTC, 09UTC, 15UTC or 21UTC, it represents a 3-hour precipitation amount.

This example shows 1.23 inches of rain.

7024624-hour precipitation amount. Follows RMK with 5 digits starting with 7. The last 4 digits are the inches of rain in hundredths.

This example shows 2.46 inches of rain.

8/765Cloud cover using WMO Code. Follows RMK starting with 8/ followed by a 3 digit number representing WMO cloud codes.
98060Duration of sunshine in minutes. Follows RMK with 5 digits starting with 98. The last 3 digits are the total minutes of sunshine.

This example indicates 60 minutes of sunshine.

931222Snowfall in the last 6-hours. Follows RMK with 6 digits starting with 931. The last 3 digits are the total snowfall in inches and tenths.

This example indicates 22.2 inches of snowfall.

933021Liquid water equivalent of the snow (SWE). Follows RMK with 6 digits starting with 933. The last 3 digits are the total inches in tenths.

This example indicates 2.1 inches SWE.

WMO codes for cloud types

The following codes identify the cloud types used in the 8/nnn part. [17]

Code Low Clouds Middle Clouds High Clouds
0nonenonenone
1Cumulus
(fair weather)
Altostratus
(thin)
Cirrus
(filaments)
2Cumulus
(towering)
Altostratus
(thick)
Cirrus
(dense)
3Cumulonimbus
(no anvil)
Altocumulus
(thin)
Cirrus
(often with Cumulonimbus)
4Stratocumulus
(from Cumulus)
Altocumulus
(patchy)
Cirrus
(thickening)
5Stratocumulus
(not Cumulus)
Altocumulus
(thickening)
Cirrus / Cirrostratus
(low in sky)
6Stratus or Fractostratus
(fair)
Altocumulus
(from Cumulus)
Cirrus / Cirrostratus
(hi in sky)
7Fractocumulus / Fractostratus
(bad weather)
Altocumulus
(with Altocumulus,
Altostratus, Nimbostratus)
Cirrostratus
(entire sky)
8Cumulus and StratocumulusAltocumulus
(with turrets)
Cirrostratus
(partial)
9Cumulonimbus
(T-storm)
Altocumulus
(chaotic)
Cirrocumulus or
Cirrocumulus / Cirrus / Cirrostratus
/not validabove overcastabove overcast

See also

References

External links

Decoding
Format specifications
Software libraries
Current reports
Current and historical reports
Wind roses based on METAR data
This article is issued from Wikipedia - version of the Saturday, April 30, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.