MET 009

Application of meteorological information

The messages at a glance

The messages this lesson covers, side by side: what each is for, how it is written and sent, and how long it lasts. Each name leads to its section.

Message	Observed or forecast	Where and what for	Written in	Sent	How often or how long
`MET REPORT` and `SPECIAL`	Observed	At the aerodrome only, for take-off and landing	Abbreviated plain language	By radio and on the ATIS	Every hour, or every half hour. A SPECIAL between two reports, if the weather changes significantly. A TREND can be added at the end: a forecast for the next 2 hours
`METAR` and `SPECI`	Observed	The aerodrome and its vicinity, within 16 km, to plan a flight	A coded format	On the AFTN	Every hour, or every half hour; in the EU every half hour at aerodromes with scheduled international commercial air transport. A SPECI between two reports, if the weather changes significantly. A TREND can be added at the end: a forecast for the next 2 hours
`TAF`	Forecast	The expected weather at an aerodrome	Code, as a METAR is	–	Valid for 9, 24 or 30 hours. A TAF AMD if the expected weather changes significantly
`SIGMET`	Observed or forecast	En-route weather, for an FIR	–	–	No longer than 4 hours (6 hours for volcanic ash or a tropical cyclone), and cancelled when the weather has ended
`AIRMET`	Observed or forecast	En-route weather for flights below FL 100, weaker than a SIGMET needs: information, not a warning. Denmark issues none	–	–	–
`ARS`	Observed	From an aircraft in flight, when it meets certain weather, such as severe icing	–	–	–
`GAMET`	Forecast	An area, for low-level flights. Denmark issues none	–	–	–

The local routine report

The MET REPORT and the SPECIAL: the weather at the aerodrome, for the traffic there.

Only used locallyUsed only at the aerodrome where the observations are made.

Sent by voice or on the ATISTransmitted verbally by radio, or on the ATIS.

Abbreviated plain languageWritten in abbreviated plain language, not in a code.

SPECIALIf the weather changes significantly between two routine reports, a special report is sent.

How often

ICAOObservations every hour, or every half hour by regional agreement.

The EUA METAR every half hour, at aerodromes with scheduled international commercial air transport.

20 and 50 pastMany countries send them at 20 and 50 minutes past the hour.

DenmarkKastrup and Billund report every half hour.

What the report holds, item by item and in order, is in The report, item by item, below.

The report, item by item

The items of a report, in order, and the instrument that measures each. One report from Kastrup, EKCH, written both ways: as a MET REPORT and as a METAR.

Item	Measured by	MET REPORT	METAR
Type of report	–	`MET REPORT`	`METAR`
Location	–	`EKCH`	`EKCH`
Time	–	`070650Z`	`070650Z`
Automated or missing reportOnly when it applies: AUTO for a report from an automatic station, NIL for a missing report. This Kastrup report is neither, so the item is left out	–	–	–
WindDirection in degrees, speed in knots	Anemometer	`WIND 220/8KT`	`22008KT`
VisibilityIn metres under 5 km, in kilometres from 5 km. A METAR: always in metres	Transmissometer or forward scatter meter	`VIS 1200M`	`1200`
RVROnly when the visibility or the RVR is less than 1 500 m. A METAR gives the touchdown zone’s value	Transmissometer or forward scatter meter	`RVR TDZ 1400M MID 1400M END 1300M`	`R22L/1400N`
Present weather	Present weather sensor	`BR`	`BR`
CloudThe amount, then the height of the base: in feet, or in a METAR in hundreds of feet	Ceilometer	`CLD BKN 500FT`	`BKN005`
Temperature and dew pointIn degrees Celsius	Thermometer; hygrometer, for the humidity	`T12 DP11`	`12/11`
QNHIn a local report, also the QFE, when it is given	Barometer, in hPa	`QNH 1012HPA`	`Q1012`
Supplementary informationRE: since the last report, but not now. With reports every half hour, that is the last 30 minutes	–	`RERA`	`RERA`
TrendA forecast for the next 2 hours, added at the end. A METAR writes it without the word TREND: The end of a report	–	`TREND NOSIG`	`NOSIG`

Each visibility sensor gives both the visibility and the RVR. The instruments and the units they report in are in MET 001.

Abbreviated plain language names each item by a word or its letters (WIND, VIS, CLD, T, DP, QNH, TREND). A coded format gives the same items, each in its place and form, with no words to name them.

Present weather

The same codes in a MET REPORT and a METAR, for example SN, snow, FG, fog, and UP, unknown precipitation. Two things differ. The intensity is written FBL, MOD and HVY in a MET REPORT, a minus sign, no sign and a plus sign in a METAR. VC, vicinity, is used only in a METAR. Each code is explained in MET 006 (precipitation) and MET 007 (the rest).

The weather codes

Intensity or proximity

FBLLightMinus sign in a METAR
MODModerateNo sign in a METAR
HVYHeavyPlus sign in a METAR
VCVicinityWithin 16 km of the aerodrome, but not on it. In a METAR only

Descriptor

MIShallowLess than 2 m above the ground
BCPatchesFog in patches, here and there over the aerodrome
PRPartialFog over a substantial part of the aerodrome, the rest clear
DRLow driftingDust, sand or snow raised by the wind to less than 2 m
BLBlowingRaised by the wind to 2 m or more
SHShowers
TSThunderstorm
FZFreezing

Precipitation

DZDrizzle
RARain
SNSnow
SGSnow grains
PLIce pellets
GRHail
GSSmall hail or snow pellets
UPUnknown precipitationAutomatic stations only: the type could not be identified

Obscuration

BRMistVisibility 1 000 to 5 000 m
FGFogVisibility less than 1 000 m
FUSmoke
VAVolcanic ash
DUDust
SASand
HZHaze

Other phenomena

PODust or sand whirls
SQSquall
FCFunnel cloud
DSDust storm
SSSandstorm

More local report groups

Wind

WIND 240/5KT VRB BTN 220/ AND 350/240°, 5 kt, varying between 220° and 350°The direction varies by 60° or more but less than 180°, at 3 kt or more: the mean and the two extremes
WIND VRB BTN 350/ AND 050/2KTVarying between 350° and 050°, 2 ktThe same, under 3 kt: the two extremes, without a mean direction
WIND VRB2KTVariable, 2 ktThe direction varies by 180° or more: VRB alone
WIND CALMCalmLess than 1 kt
WIND 310/15KT MAX35 MNM9310°, 15 kt, at most 35 kt, at least 9 ktA wind that is not constant

Visibility and RVR

VIS 5KM5 kmFrom 5 km: in kilometres. Under 5 km: in metres
RVR TDZ 400M MID 600M END 300MTouchdown zone 400 m, mid-point 600 m, stop end 300 mUsually all three parts of the runway
RVR 800M800 m at the touchdown zoneSometimes only the touchdown zone

Cloud

CLD BKN TCU 4000FTBroken towering cumulus, base 4 000 ftTCU and CB are the only cloud types named
CLD FEW CB 2000FTFew cumulonimbus, base 2 000 ft
CAVOKVisibility, cloud and present weather better than prescribed values or conditions
NSCNil significant cloud
NCDNo cloud detected

Temperature and dew point

TMS02 DPMS02Temperature −2 °C, dew point −2 °CMS: minus

What CAVOK and NSC mean is in MET 001, NCD in MET 004.

Reading a report aloud

How the numbers are said, and which words may be left out.

NumbersSingle digits, but whole hundreds and thousands for altitude, cloud height, visibility and RVR.

May be left outIf no confusion results: “surface” with the wind direction and speed; “visibility”, “cloud” and “height”; “hectopascal”.

How it startsThe report and the place, then the time. The date is left out.

How numbers are said on the radio, rule by rule, is in ATM 002.

The report from Kastrup, read aloud

MET REPORT EKCH 070650Z WIND 220/8KT VIS 1200M RVR TDZ 1400M MID 1400M END 1300M BR CLD BKN 500FT T12 DP11 QNH 1012HPA RERA TREND NOSIG

Report	Said
`MET REPORT EKCH`	“MET REPORT KASTRUP”
`070650Z`	“TIME ZERO SIX FIVE ZERO”The date, the 7th, is left out
`WIND 220/8KT`	“WIND TWO TWO ZERO DEGREES EIGHT KNOTS”“Surface” is left out
`VIS 1200M`	“ONE THOUSAND TWO HUNDRED METRES”“Visibility” is left out
`RVR TDZ 1400M MID 1400M END 1300M`	“RVR TOUCHDOWN ONE THOUSAND FOUR HUNDRED METRES, MIDPOINT ONE THOUSAND FOUR HUNDRED METRES, STOP END ONE THOUSAND THREE HUNDRED METRES”
`BR`	“MIST”
`CLD BKN 500FT`	“BROKEN FIVE HUNDRED FEET”“Cloud” and “height” are left out
`T12 DP11`	“TEMPERATURE ONE TWO, DEW POINT ONE ONE”
`QNH 1012HPA`	“QNH ONE ZERO ONE TWO”“Hectopascal” is left out
`RERA`	“RECENT RAIN”

The trend at the end, TREND NOSIG, is read as it stands.

METAR and SPECI

The coded report: the same weather as the local report, for use beyond the aerodrome.

The nameMETAR is ICAO’s aerodrome routine meteorological report. The course spells the letters out as “meteorological aviation routine weather report”.

WhereA report on the aerodrome and its vicinity, within 16 km.

Used forUsed beyond the aerodrome, to plan a flight.

SentOn the AFTN.

ContentThe same items as the MET REPORT, but coded.

SPECIIf the weather changes significantly between two reports, a SPECI is sent.

More METAR groups

Wind

00000KTCalm
10017G30KT100°, 17 kt, gusts 30 ktG: gusts
170P99KT170°, 100 kt or moreP99: more than 99 kt
35075GP99KT350°, 75 kt, gusts 100 kt or more
34016G29KT 310V030340°, 16 kt, gusts 29 kt, direction varying between 310° and 030°

Visibility

999910 km or more
3800 1700SEPrevailing 3 800 m, lowest 1 700 m to the south-east
9999NDV10 km or more, no directional variations availableNDV: added by an automatic station

RVR

R19/0350V0600RVR runway 19: between 350 and 600 m
R04L/0500 R04R/0650RVR runway 04L: 500 m, runway 04R: 650 mTwo parallel runways, a group each

RVR tendency

R01L/0750NRVR runway 01L: 750 m, no changeN: no change
R19R/P1500URVR runway 19R: more than 1 500 m, going upP: more than; U: upward
R26/M0050DRVR runway 26: less than 50 m, going downM: less than; D: downward

Cloud: amount and base, in hundreds of feet

FEW025Few, base 2 500 ftFEW: 1 to 2 oktas
SCT040Scattered, base 4 000 ftSCT: 3 to 4 oktas
BKN012Broken, base 1 200 ftBKN: 5 to 7 oktas
OVC008Overcast, base 800 ftOVC: 8 oktas

Cloud: type, and no cloud

BKN040TCUBroken towering cumulus, base 4 000 ftTCU or CB follows the group: the only cloud types named
FEW020CBFew cumulonimbus, base 2 000 ft
NSCNil significant cloud
NCDNo cloud detected

Temperature, dew point and QNH

M10−10 °CM: minus
07/M05Temperature 7 °C, dew point −5 °CThe temperature, then the dew point
Q0987QNH 987 hPa

Missing data

240//KTWind 240°, speed missingA slash for each missing figure
////Visibility missing
///05Temperature missing, dew point 5 °C

How a wind group is read, part by part, is in MET 005, and the RVR group in MET 007. The weather codes are in The report, item by item, above. The cloud amounts (FEW, SCT, BKN, OVC) and CAVOK are in MET 001, and the cloud types in MET 004. What can end a METAR, the supplementary information and the TREND, is in The end of a report, below.

The end of a report

After its items, a report can end with supplementary information and a TREND.

Supplementary information

Recent weather, wind shear and the sea

Recent weather

RERARecent rainRE: since the last report, but not now. With reports every half hour, that is the last 30 minutes. One group, in a local report and a METAR
RETSRARecent thunderstorm with rain

Wind shear

WS R27Wind shear, runway 27In a METAR. A group of its own, not a remark
WS ALL RWYWind shear on all runwaysIn a METAR

The sea

W09/S5Sea surface temperature 9 °C, state of the sea 5W: sea surface temperature; S: state of the sea. From offshore stations only

The TREND

ForecastFor the next 2 hours from the time of the report.

Not a report of its ownA TREND is part of the report it ends: a MET REPORT or a METAR.

In a MET REPORTAdded at the end, after the word TREND.

In a METARAdded at the end, without the word TREND: the change group (NOSIG, BECMG or TEMPO) follows the report straight away.

The TREND’s groups

Change groups

NOSIGNo significant change
BECMGBecoming: changes and stays
TEMPOTemporary: changes, then goes back

Times

AT1130At 11:30AT: at. After BECMG only
TL1200Until 12:00TL: till. After BECMG or TEMPO
FM1100From 11:00FM: from. After BECMG or TEMPO

NOSIGNo significant change

BECMGBecoming: changes and stays

TEMPOTemporary: changes, then goes back

Time of the report+1 h+2 h

As it moves, a time line sweeps from the time of the report to 2 hours later, and each trace is drawn behind it.

One value, such as the visibility, over the 2 hours of a TREND: BECMG changes and stays, TEMPO changes and goes back, NOSIG stays as it is.

An example

TREND BECMG AT1130 CLD OVC 1000FT

TREND: Trend forecast
BECMG: Becoming: changes and stays
AT1130: At 11:30
CLD OVC 1000FT: Cloud overcast, base 1 000 ft

At 11:30 the cloud becomes overcast at 1 000 ft, and stays so.

Decode a report

Four reports from Danish aerodromes, group by group: what each group says, and the rule behind it.

A local routine report from Kastrup, in abbreviated plain language. Click a group, or a colour below it, to see what it says.

MET REPORTIdentification

Type of report

Local routine report

Used only at the aerodrome where the observations are made, sent by voice or on the ATIS, in abbreviated plain language. If the weather changes significantly between two routine reports, a special report is sent: SPECIAL.

The first two tabs are the same weather at Kastrup: the report read aloud above, and the same report as a METAR.

TAF

The forecast for an aerodrome, and the change groups it uses.

The nameTAF is the terminal aerodrome forecast.

Expected weatherThe expected meteorological conditions at an aerodrome.

CodedWritten in code, as a METAR is.

ValidFor 9, 24 or 30 hours.

TAF AMDAn amended TAF. It is issued if the expected weather changes significantly.

The TAF’s change groups

Change groups

BECMGBecoming: changes and stays
TEMPOTemporary: changes, then goes back
FMFrom: new weather in the forecast, from that time
PROBProbability of the weather named

A TAF uses BECMG and TEMPO as a TREND does, but each is followed by its period in days and hours: BECMG 0710/0712. FM, then the day, hour and minutes, starts new weather from that time and replaces everything before it. PROB gives the probability of other weather. A TAF has no NOSIG, AT or TL. In a TREND, FM only times a BECMG or TEMPO change, and PROB is never used.

Decode a TAF

A TAF for Kastrup, one change group to a line. Click a group to see what it forecasts.

TAFIdentification and times

Type of forecast

Terminal aerodrome forecast

The expected meteorological conditions at an aerodrome, written in code, as a METAR is.

The first line, read out: Kastrup, issued on the 7th at 05:00 UTC, valid from 06:00 on the 7th to 06:00 on the 8th: wind 240° at 12 kt, visibility 10 km or more, scattered cloud at 3 000 ft.

SIGMET and other en-route messages

The SIGMET, significant meteorological information, and the other messages on the weather en route.

Its validity is normally no longer than 4 hours (6 hours for volcanic ash or a tropical cyclone), and it is cancelled as soon as the weather has ended.

Observed or forecastOBS observed, FCST forecast.

DenmarkIssues SIGMET only (MET 001).

Severe icingForecast in a SIGMET (MET 008).

Decode a SIGMET

A SIGMET for the København FIR. Click a group to see what it says.

EKDKIdentification

FIR indicator

The København FIR

The ICAO location indicator of the ATS unit serving the FIR the SIGMET is for (LAW 003).

The whole SIGMET, read out: København FIR, SIGMET I01, valid on the 15th from 09:00 to 13:00 UTC, from the Danish meteorological watch office. Severe icing was observed at 08:40 UTC and is expected to continue within an area over Jutland, between FL 60 and FL 140, moving east at 10 knots, with no change in intensity.

The en-route messages

Message	From	What it is	Limits
`SIGMET`	The meteorological watch office	Significant meteorological information. En-route weather, observed or forecast, for an FIR.	Valid no longer than 4 hours; 6 hours for volcanic ash or a tropical cyclone.
`AIRMET`	The meteorological watch office (MET 001)	Airmen’s meteorological information. En-route weather weaker than a SIGMET needs. It is information, not a warning.	Flights below FL 100. Denmark issues none (MET 001).
`ARS`	An aircraft in flight	Special air-report. A meteorological report, made when the aircraft meets certain weather, such as severe icing (MET 008).	–
`GAMET`	–	Area forecast for low-level flights.	Denmark issues none.

SNOWTAM and broadcasts

The SNOWTAM, and three services that broadcast information to aircraft.

Name	What it is
`SNOWTAM`	Special series NOTAM on snow, ice, slush, frost or standing water. Read and decoded in LAW 006.
`ATIS`	Automatic terminal information service. One way a local report reaches aircraft. A transition level can come by ATIS, too (ATM 002).
`VOLMET`	Meteorological information for aircraft in flight.
`OFIS`	Operational flight information service. Sent out as broadcasts.

The upper wind and temperature chart

The forecast wind and temperature at one flight level, as an arrow and a figure at each point of a grid.

Drawn, not a real chart. Each arrow points to where the wind comes from.

The arrowRuns out from the grid point towards where the wind comes from. The barbs are at its outer end.

The speedAdd up the barbs: a half barb is 5 kt, a full barb 10 kt and a pennant 50 kt. An arrow with no barbs is calm.

The temperatureRead as minus, unless it is marked PS, for plus: 04 is minus 4 °C, PS03 is plus 3 °C.

The ringed point reads 045/10, 04: a north-east wind at 10 knots, from 045°, and minus 4 °C.

Reading the arrows and the figures

Speeds

CalmNo barbs
5 ktHalf barb
10 ktFull barb
15 kt10 + 5
20 kt10 + 10
50 ktPennant
65 kt50 + 10 + 5

Readings

045/10
270/15
180/20
320/35
090/50
230/65

Temperatures

22Minus 22 °C
04Minus 4 °C
PS03Plus 3 °C

The significant weather chart

The SIGWX chart: issued by the world area forecast centres (MET 001), it shows the weather that matters most to air transport.

Drawn, not a real chart: a chart for FL 250 to FL 630, north at the top, its CAT key at the side.

The course teaches this form. Since January 2025 the world area forecast centres’ charts reach FL 600, show no embedded CB and no CB base, draw the tropopause as contours and mark turbulence areas; surface fronts are drawn on charts that start at the surface.

Reading the chart

Jet streamA bold arrow along its core, in the direction of the wind. Its barbs give the speed, added up as on the upper wind chart, and its flight level is printed beside it: here 110 kt at FL 340. Jet streams are in MET 005.
Clear air turbulence (CAT)Dashed lines enclose areas of similar turbulence. A number in a box points to the key, which gives the intensity, then the top over the base: 370/290 is from FL 290 to FL 370. XXX as the top means above the chart.
Tropopause heightsFlight levels in boxes. A box pointing up, marked H, is a high of the tropopause; a box pointing down, marked L, is a low.
CB areasScalloped lines ring an area of CB, with a label such as ISOL EMBD CB 380/XXX: isolated CB, embedded in layer cloud (MET 008), top FL 380, base below the chart. The course writes EMB for embedded.
FrontsThe four fronts at the surface: cold, warm, occluded and quasi-stationary. They are drawn as in MET 005, which calls the quasi-stationary front the stationary front.
VolcanoesAn active volcano is shown with its name and position. The latest SIGMET gives more.

On the chart, a CB implies thunderstorm, hail, and moderate or severe turbulence and icing.

The symbols

Icing, turbulence and storms

Moderate icing
Severe icing
Moderate turbulence
Severe turbulence
Thunderstorms
Freezing precipitation

Precipitation

Drizzle
Rain
Snow
Shower
Hail

Widespread

Widespread mist
Widespread fog
Widespread blowing snow

Fronts at the surface

Cold front
Warm front
Occluded front
Quasi-stationary front

The symbols as the course draws them; the fronts in the colours of MET 005.

The icing and turbulence symbols, with what each level means, are in MET 008’s severity table.

Reading material

Meteorology

MET 009 Application of Meteorological Information PowerPoint / PDF

EPN Group Training Document Meteorology, chapter 9 Reading list, course material

European Union Aviation Safety Agency, Easy Access Rules for Air Traffic Management/Air Navigation Services (Regulation (EU) 2017/373), March 2025 Reference, free

WMO-No. 306, Manual on Codes, International Codes, Volume I.1, Part A: Alphanumeric Codes, 2019 edition Reference, free

International Civil Aviation Organization, Annex 3, Meteorological Service for International Air Navigation, 21st edition, August 2025 Reference, paid

International Civil Aviation Organization, Procedures for Air Navigation Services: Meteorology (PANS-MET), Doc 10157, 1st edition, 2025 Reference, paid

International Civil Aviation Organization, Manual of Aeronautical Meteorological Practice, Doc 8896, 9th edition, 2011 Reference, free