How to Decode METAR, TAF, and pilot reports.

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A METAR is a codified observation message indicating an airfield weather conditions observed at a given time.

Such a message is established every hour.

 

A SPECI message is identical to a METAR but is established punctually instead of regularly. It is a special observation message highlighting any significant change since the last METAR or SPECI was issued.

 

A TAF is a terminal forcast.  It is issued every few hours, and is updated if necessary sooner.

 

Aviation Routine Weather Report (METAR)

 

Example:

METAR

KRNO

210056Z

05012KT

10SM

-SN

BKN050

02/M08

A3016

RMK AO2 SLP228

T00221083

1

2

3

4

5

6

7

8

9

10

11

 

1.     Message Type

·         METAR: routine weather report

·         SPECI: special weather report, triggered by a weather change

·         AUTO will be first item for ASOS/AWOS generated reports

2.     ICAO Identifier (4-letter)

3.     Issuance Time DDHHMMz (UTC)

·         COR (CCD in Canada) if correction to observation

4.     Wind

·         First 3 digits: True Wind direction or average if variable (VRB).

Note: If the wind direction varies 60° or more, the direction will be indicated with a V (e.g. 180V250)

·         Next 2 digits: Mean speed and units

-        KT=knots, KMH=kilometers/hour, MPS=meters/second

·         G (gust) as needed – 2 or 3 digit maximum speed

·         Calm will be indicated by 00000KT

·         Example: 18012G22KT 150V240

5.     Horizontal Visibility

·         Prevailing Visibility (PV)

-        Statue miles (SM) and fractions (US & Canada only) or,

-        4 digit minimum visibility in meters, and,

-        Lowest value and direction, as required (shown as a remark)


 

 

·         Runway Visual Range (RVR)

-        R: Runway Designator, L/R/C as needed, “/”

-        P/M: Plus/Minus (US only)

-        4 digit value (feet/meters)

-        V (variability) with tendency U/D/N (up/down/no change)

-        Example: R18R/1200FTV/U

6.     Present Weather (Constructed sequentially):

·         Intensity

·         Descriptor

·         Precipitation (Dominant type is listed first if more than one type reported)

·         Obscuration

·         Other

 

 

Qualifier

Weather Phenomena

Intensity or Proximity

Descriptor

Precipitation

Obscuration

Other

Light

BC

Patches

DZ

Drizzle

BR

Mist (1)

DS

Duststorm

BL

Blowing (2)

GR

Hail (3)

DU

Widespread Dust

No qualifier

Moderate

DR

Low Drifting (4)

GS

Small Hail and/or snow pellets (5)

FG

Fog (6)

FC

Funnel Clouds

FZ

Freezing

IC

Ice Crystals

FU

Smoke

PO

Dust/Sand Whirls

+

Heavy

MI

Shallow

PL

Ice Pellets

HZ

Haze

SQ

Squall(s)

PR

Partial

RA

Rain

SA

Sand

VC

Vicinity (7)

SH

Shower(s)

SG

Snow Grains

VA

Volcanic Ash

SS

Sandstorm

TS

Thunderstorm

SN

Snow

 

UP

Unknown Precipitation

(1)    Visibility at least 1000m (5/8SM) but not more than 9600m (6SM)

(2)    6 feet or more above the ground

(3)    Hailstone diameter 5mm or greater

(4)    Less than 6 feet above the ground

(5)    Hailstone diameter less than 5mm

(6)    Visibility less than 1000m (5/8SM)

(7)    Within 8KM (5SM) of the aerodrome but not at the aerodrome

 


 

7.     Sky Cover

·         Cloud Description

-        Amount in eights (octas)

SKC=Sky Clear (clear below 12,000 for ASOS/AWOS)

NSC=No significant clouds

FEW=Few (1/8 to 2/8 sky cover)

SCT=Scattered (3/8 to 4/8 sky cover)

BKN=Broken (5/8 to 7/8 sky cover)

OVC=Overcast (8/8 sky cover)

8.     Terperature/Dewpoint (whole °C) (preceded by M=minus)

·         First 2 digits = temperature

·         Second 2 digits = dewpoint

9.     Altimeter setting (QNH) and indicator (A=InHg, Q=hPa)

10. Supplementary Information

·         RE = Recent weather followed by weather codes

·         WS = Windshear, followed by:

-        TKOF/LDG (takeoff/landing)

-        RWY (2 digits runway identifier and designator L/R/C)

·         RMK = Remark

-        SLP = Sea Level Pressure

-        T00221083 (Expanded temp/dewpoint)

1st, 5th digits: 0=plus, 1=minus

2nd-4th digits: temp (decimal missing) (02.2)

6th-8th digits: dewpoint (decimal missing) (-8.3)

11. Trend Forecast (2 hours from time of observation) (Not used in US)

·         PROB and 2 digits (30 or 40) = probability 30% or 40%

·         Used to indicate the probability of occurance of alternate element(s) or temporary fluctuations

·         Change Indicator

-        BECMG = Becoming (used where changes are expected to reach or pass through specified values

-        TEMPO = Temporary (fluctuations of less than one hour duration

-        NOSIG = No significant change


 

·         Forecast Wind (same as item 4)

·         Forecast Visibility (as item 5) (9999 indicates 10Kilometers vis or greater)

·         Forecast Weather (as item 6)

·         Forecast Cloud (as item 7)

 

EIGHT FIGURE GROUP

An eight digit telegraphic code on runway conditions for some European airports may be included at the end of hourly METAR messages:

Eight Figure Group

1st two digits

Runway designator

3rd digit

Runway deposits

4th digit

Extent of runway contamination

5th and 6th digits

Depth of deposit

7th and 8th digits

Friction coefficient or braking action

 

The first two digits correspond to the runway designator.  For parallel runways LEFT is indicated by the designator only (18L would be displayed as 18) and RIGHT has 50 added (18R would be displayed as 68).  When all runways are affected the figure group 88 will be used.  If 99 appears as the first two digits the information is a repetition of the last message because no new message has been received in time for transmission.

 

Runway Deposits

Extent of Runway Contamination

Depth of Deposit

0

Clear & Dry

1

<10% contaminated (covered)

00

Less than 1mm

1

Damp

2

11% to 25% contaminated (covered)

01-90

Measurement in mm

2

Wet or water particles

92

10cm

3

Rime or frost covered (normally > 1mm)

5

26%-50% contaminated (covered)

93

15cm

4

Dry Snow

9

51%-100% contaminated (covered)

94

20cm

5

Wet Snow

95

25cm

6

Slush

/

Not reported (runway clearance in progress)

96

30cm

7

Ice

97

35cm

8

Compacted or rolled snow

 

 

98

40cm or more

9

Frozen ruts or ridges

 

 

99

Runway not operational due to snow, slush, ice, large drifts or runway clearance, depth not reported

/

Not reported (runway clearance in progress)

 

 

//

Not operationally significant or not measurable

Note: the quoted depth is the mean of a number of reading or if operationally significant the greatest depth measured.


 

 

Friction Coefficient or Braking Action (7th and 8th digits)

28

Friction coefficient 0.28

35

Friction coefficient 0.35

91

Braking action poor

92

Braking action medium to poor

93

Braking action medium

94

Braking action medium to good

95

Braking action good

99

Figures unreliable

//

Braking action not reported or runway not operations or airport closed.

Note: Where braking action is assessed at a number of points along the runway the mean value will be transmitted or if operationally significant the lowest value.

If measuring equipment does not allow measurement of friction with satisfactory reliability (such as contaminated by wet snow, slush or loose snow) the figure 99 will be used.

 

Automated Surface/Weather Observation System (ASOS/AWOS)

 

The Automated Surface Observation System (ASOS) and Automated Weather Observation System (AWOS) observe and report altimeter setting, wind direction and speed, temperature, dewpoint, visibility and ceiling/cloud height.  Pilots may use automated weather observation from ASOS/AWOS, provided the observations from ASOS/AWOS, provided the observation includes all necessary weather parameters, and that the system is installed, operated and maintained according to applicable FAA standards.

Pilots may obtain the ASOS/AWOS reports through written, radio or telephone methods.  Refer to METAR section for ASOS/AWOS report format.

ASOS/AWOS observations may not be used as an authorized weather observation if either the visibility or the wind is reported as missing.

ASOS/AWOS observation are unusable for the purpose of initiating or conducting an instrument approach if the altimeter setting is reported as missing unless an approved alternate source is noted on the applicable approach chart.


 

 

TAF

Example:

TAF

KRNO

202320Z

210024

04010G20KT

P6SM

-SN

SCT060

1

2

3

4

5

6

7

8

 

FM0300

05008KT

P6SM

SCT060

9

 

 

 

 

1.     Type of report (TAF)

2.     ICAO Identifier (4 letter)

3.     Issuance time (DDHHMMZ) UTC.  May precede ICAO identifier at some airports.

4.     Day (DD).  Hour begins (1st two digits XX) Hour ends (2nd two digits).

5.     Wind. First 3 digits true wind direction or average if variable.  If the wind varies 60° or more, the direction will be indicated with a V (e.g. 120V190).  Next two digits Mean speed and units (KT=knots, KMH=kilometers per hour, or MPS=meters per second).  G=gust as needed (2 or 3 digits).  Calm will be indicated by 00000XXX (XXX will be replaced by the appropriate units).

6.     Horizontal visibility.

a.      Prevailing visibility (PV)

-        Statute Miles (SM) and fractions (US only), or

-        4 digit minimum visibility in meters, and

-        Lowest value and direction, as required

b.     Runway Visual Range (RVR)

-        R=Runway Designator, L/R/C as needed, “/”

-        P/M=Plus/Minus (US Only)

-        4 digit value (feet/meters)

-        V(variability) with tendency U/D/N (up/down/no change)

7.     Present Weather (constructed sequentially):

·         Intensity

·         Descriptor

·         Precipitation (Dominant type is listed first if more than one type reported)

·         Obscuration

·         Other

 

 

Qualifier

Weather Phenomena

Intensity or Proximity

Descriptor

Precipitation

Obscuration

Other

Light

BC

Patches

DZ

Drizzle

BR

Mist (1)

DS

Duststorm

BL

Blowing (2)

GR

Hail (3)

DU

Widespread Dust

No qualifier

Moderate

DR

Low Drifting (4)

GS

Small Hail and/or snow pellets (5)

FG

Fog (6)

FC

Funnel Clouds

FZ

Freezing

IC

Ice Crystals

FU

Smoke

PO

Dust/Sand Whirls

+

Heavy

MI

Shallow

PL

Ice Pellets

HZ

Haze

SQ

Squall(s)

PR

Partial

RA

Rain

SA

Sand

VC

Vicinity (7)

SH

Shower(s)

SG

Snow Grains

VA

Volcanic Ash

SS

Sandstorm

TS

Thunderstorm

SN

Snow

 

UP

Unknown Precipitation

(8)    Visibility at least 1000m (5/8SM) but not more than 9600m (6SM)

(9)    6 feet or more above the ground

(10)Hailstone diameter 5mm or greater

(11)Less than 6 feet above the ground

(12)Hailstone diameter less than 5mm

(13)Visibility less than 1000m (5/8SM)

(14)Within 8KM (5SM) of the aerodrome but not at the aerodrome

 

8.     Sky Cover

·         Cloud Description

-        Amount in eights (octas)

SKC=Sky Clear (clear below 12,000 for ASOS/AWOS)

NSC=No significant clouds

FEW=Few (1/8 to 2/8 sky cover)

SCT=Scattered (3/8 to 4/8 sky cover)

BKN=Broken (5/8 to 7/8 sky cover)

OVC=Overcast (8/8 sky cover)

-        Height: 100s of feet (30m)

-        Type CB (Cumulonimbus) or TCU (Towering cumulus) only.

·         CAVOK – Ceiling and visibility OK (not used in US).  Replaces visibility/RVR, present weather, and clouds if:

-        Visibility is 10KM or greater

-        No CB and no cloud below 1500M (5000ft) or below highest minimum sector altitude whichever is greater, and

-        No precipitation, thunderstorm, sandstorm, duststorm, shallow fog, or low drifting dust/sand/snow.

·         Vertical visibility (when sky obscured) – VV100’s of feet (30m) (VV /// means vertical visibility unavailable)

Optional groups (Forecast icing, Turbulence, & Temperature)

T= Temperature group indicator

Temperature: two digits (if below 0°, will be preceded by “M”),”/”

Expected time temperature will be reached: 2 digits, Z.

Icing Layer(s): 6 digits for each icing group (6WXXXY). 

6: first digit of the icing group is always a 6.

Icing type: Second digit:

 

Icing Intensity

Location

0

None

None

1

Light Icing

 

2

Light Icing

In cloud

3

Light Icing

In precipitation

4

Moderate

 

5

Moderate

In cloud

6

Moderate

In precipitation

7

Severe

 

8

Severe

In cloud

9

Severe

In precipitation

Icing layer’s base: next 3 digits.  (direct reading in 100s of ft/30s meters)

Thickness of icing layer: last digit:

 

Thickness of Layer

0

Up to top of cloud

1

300m/1000’

2

600m/2000’

3

900m/2000’

4

1200m/4000’

5

1500m/5000’

6

1800m/6000’

7

2100m/7000’

8

2400m/8000’

9

2700m/9000’

 

Turbulence Layer(s): 6 Digits (5WXXXY)

5: first digit of the turbulence group is always a 6.

Turbulence type: Second digit:

 

Intensity

Weather Condition

Frequency

0

None

 

 

1

Light

 

 

2

Moderate

Clear

Occasional

3

Moderate

Clear

Frequent

4

Moderate

Cloud

Occasional

5

Moderate

Cloud

Frequent

6

Severe

Clear

Occasional

7

Severe

Clear

Frequent

8

Severe

Cloud

Occasional

9

Severe

Cloud

Frequent

Turbulence layer’s base: next 3 digits.  (direct reading in 100s of ft/30s meters)

Thickness of turbulence layer: last digit:

 

Thickness of Layer

0

Up to top of cloud

1

300m/1000’

2

600m/2000’

3

900m/2000’

4

1200m/4000’

5

1500m/5000’

6

1800m/6000’

7

2100m/7000’

8

2400m/8000’

9

2700m/9000’

 


 

 

SIGNIFICANT CHANGES IN FORECAST

1.     Probability groups(s)

-        PROB and 2 digits (30 or 40).

-        Probability 30% or 40% used to indicate the probability of occurrence of alternate element(s) or temporary fluctuations.  (US will only use 40%).  May also be listed as TEMPO by some non US weather services.

-        TIME (beginning 2 digits, ending 2 digits)

-        Forecast weather phenomena.

2.     Forecast Change

o       Indicators

§         BCMG=Becoming (used when changes are expected to reach or pass through specified values)

§         FM = From and 2 digit time

§         TO = To and 2 digit time

§         TEMPO = Temporary fluctuation

o       Forecast weather phenomena.


 

 

METAR /TAF Abbreviations / Cloud Types

 

A

Hail

 

AMOS

Automatic Meteorological observing system

ABM

Abeam

 

ABV

Above

 

AMS

Air mass

AC

Altocumulus

 

ANLYS

Analysis

ACCAS

Altocumulus castellanus

 

AO1

Automated observation with no precip discriminator (rain/snow)

ACCUM

Altocumulate

 

ACLD

Above clouds

 

AO2

Automated observation with precip discriminator (rain/snow)

ACSL

Standing lenticular altocumulus

 

ACTV

Active

 

AOA

At or above

ACYC

Anticyclonic

 

AOB

At or below

ADDN

Addition

 

AP

Anomalous propagation

ADRNDCK

Adirondack

 

APCH

Approach

ADVCTN

Advection

 

APRNT

Apparent

ADVY

Advisory

 

AS