Aviation Routine Weather Report (METAR)
A METAR is an observation of current surface weather
reported in a standard international format. While the
METAR code has been adopted worldwide, each country is
allowed to make modifications to the code. Normally, these
differences are minor but necessary to accommodate local
procedures or particular units of measure. This discussion of
METAR covers elements used in the United States.
METARs are issued on a regularly scheduled basis unless
significant weather changes have occurred. A special
METAR (SPECI) can be issued at any time between routine
METAR reports.
Example:
METAR KGGG 161753Z AUTO 14021G26KT 3/4SM
+TSRA BR BKN008 OVC012CB 18/17 A2970 RMK
PRESFR
A typical METAR report contains the following information
in sequential order:
1. Type of report—there are two types of METAR
reports. The first is the routine METAR report that is
transmitted on a regular time interval. The second is
the aviation selected SPECI. This is a special report
that can be given at any time to update the METAR for
rapidly changing weather conditions, aircraft mishaps,
or other critical information.
2. Station identifier—a four-letter code as established by
the International Civil Aviation Organization (ICAO).
In the 48 contiguous states, a unique three-letter
identifier is preceded by the letter “K.” For example,
Gregg County Airport in Longview, Texas, is
identified by the letters “KGGG,” K being the country
designation and GGG being the airport identifier.
In other regions of the world, including Alaska and
Hawaii, the first two letters of the four-letter ICAO
identifier indicate the region, country, or state. Alaska
identifiers always begin with the letters “PA” and
Hawaii identifiers always begin with the letters “PH.”
Station identifiers can be found by calling the FSS, a
NWS office, or by searching various websites such
as DUATS and NOAA's Aviation Weather Aviation
Digital Data Services (ADDS).
3. Date and time of report—depicted in a six-digit group
(161753Z). The first two digits are the date. The last
four digits are the time of the METAR/SPECI, which
is always given in coordinated universal time (UTC).
A “Z” is appended to the end of the time to denote
the time is given in Zulu time (UTC) as opposed to
local time.
4. Modifier—denotes that the METAR/SPECI came from
an automated source or that the report was corrected. If
the notation “AUTO” is listed in the METAR/SPECI,
the report came from an automated source. It also lists
“AO1” (for no precipitation discriminator) or “AO2”
(with precipitation discriminator) in the “Remarks”
section to indicate the type of precipitation sensors
employed at the automated station.
When the modifier “COR” is used, it identifies a
corrected report sent out to replace an earlier report
that contained an error (for example: METAR KGGG
161753Z COR).
5. Wind—reported with five digits (14021KT) unless
the speed is greater than 99 knots, in which case the
wind is reported with six digits. The first three digits
indicate the direction the true wind is blowing from in
tens of degrees. If the wind is variable, it is reported
as “VRB.” The last two digits indicate the speed of
the wind in knots unless the wind is greater than 99
knots, in which case it is indicated by three digits. If
the winds are gusting, the letter “G” follows the wind
speed (G26KT). After the letter “G,” the peak gust
recorded is provided. If the wind direction varies more
than 60° and the wind speed is greater than six knots,
a separate group of numbers, separated by a “V,” will
indicate the extremes of the wind directions.
6. Visibility—the prevailing visibility (¾ SM) is reported
in statute miles as denoted by the letters “SM.” It is
reported in both miles and fractions of miles. At times,
runway visual range (RVR) is reported following the
prevailing visibility. RVR is the distance a pilot can
see down the runway in a moving aircraft. When RVR
is reported, it is shown with an R, then the runway
number followed by a slant, then the visual range
in feet. For example, when the RVR is reported as
R17L/1400FT, it translates to a visual range of 1,400
feet on runway 17 left.
7. Weather—can be broken down into two different
categories: qualifiers and weather phenomenon
(+TSRA BR). First, the qualifiers of intensity,
proximity, and the descriptor of the weather are given.
The intensity may be light (–), moderate ( ), or heavy
(+). Proximity only depicts weather phenomena that
are in the airport vicinity. The notation “VC” indicates
a specific weather phenomenon is in the vicinity
of five to ten miles from the airport. Descriptors
are used to describe certain types of precipitation
and obscurations. Weather phenomena may be
reported as being precipitation, obscurations, and
other phenomena, such as squalls or funnel clouds.
Intensity or Proximity 1 Precipitation 3 Obscuration 4 Other 5Descriptor 2
– Light
Moderate (no qualifier)
+ Heavy
VC in the vicinity
MI Shallow
BC Patches
DR Low drifting
BL Blowing
SH Showers
TS Thunderstorms
FZ Freezing
PR Partial
DZ Drizzle
RA Rain
SN Snow
SG Snow grains
IC Ice crystals (diamond dust)
PL Ice pellets
GR Hail
GS Small hail or snow pellets
UP *Unknown precipitation
BR Mist
FG Fog
FU Smoke
DU Dust
SA Sand
HZ Haze
PY Spray
VA Volcanic ash
PO Dust/sand whirls
SQ Squalls
FC Funnel cloud
+FC Tornado or waterspout
SS Sandstorm
DS Dust storm
The weather groups are constructed by considering columns 1–5 in this table in sequence:
intensity, followed by descriptor, followed by weather phenomena (e.g., heavy rain showers(s) is coded as +SHRA).
* Automated stations only
Qualifier Weather Phenomena
Figure 13-5. Descriptors and weather phenomena used in a typical METAR.
Contraction
SKC, CLR, FEW
FEW
SCT
BKN
OVC
Sky Cover
Less than 1∕8 (Clear)
1∕8–2∕8 (Few)
³∕8–4∕8 (Scattered)
5∕8–7∕8 (Broken)
8∕8 or (Overcast)
Figure 13-6. Reportable contractions for sky condition.
Descriptions of weather phenomena as they begin or
end and hailstone size are also listed in the “Remarks”
sections of the report. [Figure 13-5]
8. Sky condition—always reported in the sequence of
amount, height, and type or indefinite ceiling/height
(vertical visibility) (BKN008 OVC012CB, VV003).
The heights of the cloud bases are reported with a
three-digit number in hundreds of feet AGL. Clouds
above 12,000 feet are not detected or reported by an
automated station. The types of clouds, specifically
towering cumulus (TCU) or cumulonimbus (CB)
clouds, are reported with their height. Contractions
are used to describe the amount of cloud coverage and
obscuring phenomena. The amount of sky coverage is
reported in eighths of the sky from horizon to horizon.
[Figure 13-6]
9. Temperature and dew point—the air temperature and
dew point are always given in degrees Celsius (C) or
(18/17). Temperatures below 0 °C are preceded by
the letter “M” to indicate minus.
10. Altimeter setting—reported as inches of mercury
("Hg) in a four-digit number group (A2970). It is
always preceded by the letter “A.” Rising or falling
pressure may also be denoted in the “Remarks”
sections as “PRESRR” or “PRESFR,” respectively.
11. Zulu time—a term used in aviation for UTC, which
places the entire world on one time standard.
12. Remarks—the remarks section always begins with the
letters “RMK.” Comments may or may not appear in
this section of the METAR. The information contained
in this section may include wind data, variable
visibility, beginning and ending times of particular
phenomenon, pressure information, and various other
information deemed necessary. An example of a
remark regarding weather phenomenon that does not
fit in any other category would be: OCNL LTGICCG.
This translates as occasional lightning in the clouds
and from cloud to ground. Automated stations also use
the remarks section to indicate the equipment needs
maintenance.
Example:
METAR KGGG 161753Z AUTO 14021G26KT 3/4SM
+TSRA BR BKN008 OVC012CB 18/17 A2970 RMK
PRESFR
1
2
3
4
5
6
7
8
9
10
11
12
13
XXX
UA
/OV
/TM
/FL
/TP
/SK
/WX
/TA
/WV
/TB
/IC
/RM
3-letter station identifier
Routine PIREP, UUA-Urgent PIREP.
Location
Time
Altitude/flight level
Type aircraft
Sky cover/cloud layers
Weather
Air temperature in celsius (C)
Wind
Turbulence
Icing
Remarks
Nearest weather reporting location to the reported phenomenon
Use 3-letter NAVAID idents only.
a. Fix: /OV ABC, /OV ABC 090025.
b. Fix: /OV ABC 045020-DEF, /OV ABC-DEF-GHI
4 digits in UTC: /TM 0915.
3 digits for hundreds of feet. If not known, use UNKN: /FL095, /FL310, /FLUNKN.
4 digits maximum. If not known, use UNKN: /TP L329, /TP B727, /TP UNKN.
Describe as follows:
a. Height of cloud base in hundreds of feet. If unknown, use UNKN.
b. Cloud cover symbol.
c. Height of cloud tops in hundreds of feet.
Flight visibility reported first:
Use standard weather symbols:
/WX FV02SM RA HZ, /WX FV01SM TSRA.
If below zero, prefix with a hyphen: /TA 15, /TA M06.
Direction in degrees magnetic north and speed in six digits:
/WV270045KT, WV 280110KT.
Use standard contractions for intensity and type (use CAT or CHOP when
appropriate). Include altitude only if different from /FL, /TB EXTRM, /TB
LGT-MOD BLO 090.
Describe using standard intensity and type contractions. Include altitude only if
different than /FL: /IC LGT-MOD RIME, /IC SEV CLR 028-045.
Use free form to clarify the report and type hazardous elements first:
/RM LLWS -15KT SFC-030 DURC RY22 JFK.
Encoding Pilot Weather Reports (PIREPS)
Figure 13-7. PIREP encoding and decoding.
Explanation:
Routine METAR for Gregg County Airport for the 16th
day of the month at 1753Z automated source. Winds are
140 at 21 knots gusting to 26. Visibility is ¾ statute mile.
Thunderstorms with heavy rain and mist. Ceiling is broken
at 800 feet, overcast at 1,200 feet with cumulonimbus clouds.
Temperature 18 °C and dew point 17 °C. Barometric pressure
is 29.70 "Hg and falling rapidly.
Pilot Weather Reports (PIREPs)
PIREPs provide valuable information regarding the
conditions as they actually exist in the air, which cannot be
gathered from any other source. Pilots can confirm the height
of bases and tops of clouds, locations of wind shear and
turbulence, and the location of inflight icing. If the ceiling is
below 5,000 feet, or visibility is at or below five miles, ATC
facilities are required to solicit PIREPs from pilots in the area.
When unexpected weather conditions are encountered, pilots
are encouraged to make a report to a FSS or ATC. When a
pilot weather report is filed, the ATC facility or FSS adds it
to the distribution system to brief other pilots and provide
inflight advisories.
PIREPs are easy to file and a standard reporting form outlines
the manner in which they should be filed. Figure 13-7 shows
the elements of a PIREP form. Item numbers 1 through 5 are
required information when making a report, as well as at least
one weather phenomenon encountered. A PIREP is normally
transmitted as an individual report but may be appended to
a surface report. Pilot reports are easily decoded, and most
contractions used in the reports are self-explanatory.
Example:
UA/OV GGG 090025/TM 1450/FL 060/TP C182/SK
080 OVC/WX FV04SM RA/TA 05/WV 270030KT/TB
LGT/RM HVY RAIN
Explanation:
Type: .................................Routine pilot report
Location: .......................... 25 NM out on the 090° radial,
Gregg County VOR
Time: ................................ 1450 Zulu
Altitude or Flight Level: 6,000 feet
Aircraft Type: ................... Cessna 182
Sky Cover: ........................ 8,000 overcast
Visibility/Weather: ........... 4 miles in rain
Temperature: .....................5 °Celsius
Wind: ................................ 270° at 30 knots
Turbulence: .......................Light
Icing: ................................ None reported
Remarks: .......................... Rain is heavy
7. Forecast significant weather—weather phenomena
are coded in the TAF reports in the same format as
the METAR.
8. Forecast sky condition—given in the same format as
the METAR. Only cumulonimbus (CB) clouds are
forecast in this portion of the TAF report as opposed
to CBs and towering cumulus in the METAR.
9. Forecast change group—for any significant weather
change forecast to occur during the TAF time period,
the expected conditions and time period are included
in this group. This information may be shown as from
(FM), and temporary (TEMPO). “FM” is used when a
rapid and significant change, usually within an hour, is
expected. “TEMPO” is used for temporary fluctuations
of weather, expected to last less than 1 hour.
10. PROB30—a given percentage that describes the
probability of thunderstorms and precipitation
occurring in the coming hours. This forecast is not
used for the first 6 hours of the 24-hour forecast.
Example:
TAF
KPIR 111130Z 1112/1212
TEMPO 1112/1114 5SM BR
FM1500 16015G25KT P6SM SCT040 BKN250
FM120000 14012KT P6SM BKN080 OVC150 PROB30
1200/1204 3SM TSRA BKN030CB
FM120400 1408KT P6SM SCT040 OVC080
TEMPO 1204/1208 3SM TSRA OVC030CB
Explanation:
Routine TAF for Pierre, South Dakota…on the 11th day of
the month, at 1130Z…valid for 24 hours from 1200Z on the
11th to 1200Z on the 12th…wind from 150° at 12 knots…
visibility greater than 6 SM…broken clouds at 9,000 feet…
temporarily, between 1200Z and 1400Z, visibility 5 SM in
mist…from 1500Z winds from 160° at 15 knots, gusting
to 25 knots visibility greater than 6 SM…clouds scattered
at 4,000 feet and broken at 25,000 feet…from 0000Z wind
from 140° at 12 knots…visibility greater than 6 SM…clouds
broken at 8,000 feet, overcast at 15,000 feet…between 0000Z
and 0400Z, there is 30 percent probability of visibility 3
SM…thunderstorm with moderate rain showers…clouds
broken at 3,000 feet with cumulonimbus clouds…from
0400Z…winds from 140° at 8 knots…visibility greater than
6 miles…clouds at 4,000 scattered and overcast at 8,000…
temporarily between 0400Z and 0800Z…visibility 3 miles…
thunderstorms with moderate rain showers…clouds overcast
at 3,000 feet with cumulonimbus clouds…end of report (=).
Aviation Forecasts
Observed weather condition reports are often used in the
creation of forecasts for the same area. A variety of different
forecast products are produced and designed to be used in the
preflight planning stage. The printed forecasts that pilots need
to be familiar with are the terminal aerodrome forecast (TAF),
aviation area forecast (FA), inflight weather advisories
(SIGMET, AIRMET), and the winds and temperatures aloft
forecast (FB).
Terminal Aerodrome Forecasts (TAF)
A TAF is a report established for the five statute mile
radius around an airport. TAF reports are usually given for
larger airports. Each TAF is valid for a 24 or 30-hour time
period and is updated four times a day at 0000Z, 0600Z,
1200Z, and 1800Z. The TAF utilizes the same descriptors
and abbreviations as used in the METAR report. The TAF
includes the following information in sequential order:
1. Type of report—a TAF can be either a routine forecast
(TAF) or an amended forecast (TAF AMD).
2. ICAO station identifier—the station identifier is the
same as that used in a METAR.
3. Date and time of origin—time and date (081125Z)
of TAF origination is given in the six-number code
with the first two being the date, the last four being
the time. Time is always given in UTC as denoted by
the Z following the time block.
4. Valid period dates and times—The TAF valid period
(0812/0912) follows the date/time of forecast origin
group. Scheduled 24 and 30 hour TAFs are issued
four times per day, at 0000, 0600, 1200, and 1800Z.
The first two digits (08) are the day of the month for
the start of the TAF. The next two digits (12) are the
starting hour (UTC). 09 is the day of the month for
the end of the TAF, and the last two digits (12) are
the ending hour (UTC) of the valid period. A forecast
period that begins at midnight UTC is annotated as 00.
If the end time of a valid period is at midnight UTC,
it is annotated as 24. For example, a 00Z TAF issued
on the 9th of the month and valid for 24 hours would
have a valid period of 0900/0924.
5. Forecast wind—the wind direction and speed forecast
are coded in a five-digit number group. An example
would be 15011KT. The first three digits indicate the
direction of the wind in reference to true north. The
last two digits state the windspeed in knots appended
with “KT.” Like the METAR, winds greater than 99
knots are given in three digits.
6. Forecast visibility—given in statute miles and may
be in whole numbers or fractions. If the forecast is
greater than six miles, it is coded as “P6SM.”
and implies there may be occurrences of severe or greater
turbulence, severe icing, low-level wind shear, and IFR
conditions. The final line of the precautionary statement alerts
the user that heights, for the most part, are MSL. Those that
are not MSL will state AGL or CIG.
3. Synopsis—gives a brief summary identifying the
location and movement of pressure systems, fronts,
and circulation patterns.
Example:
SYNOPSIS…LOW PRES TROF 10Z OK/TX PNHDL AREA
FCST MOV EWD INTO CNTRL-SWRN OK BY 04Z.
WRMFNT 10Z CNTRL OK-SRN AR-NRN MS FCST LIFT
NWD INTO NERN OK-NRN AR EXTRM NRN MS BY 04Z.
Explanation:
As of 1000Z, there is a low pressure trough over the Oklahoma
and Texas panhandle area, which is forecast to move eastward
into central to southwestern Oklahoma by 0400Z. A warm
front located over central Oklahoma, southern Arkansas, and
northern Mississippi at 1000Z is forecast to lift northwestward
into northeastern Oklahoma, northern Arkansas, and extreme
northern Mississippi by 0400Z.
4. VFR Clouds and Weather—This section lists expected
sky conditions, visibility, and weather for the next 12
hours and an outlook for the following 6 hours.
Example:
S CNTRL AND SERN TX
AGL SCT-BKN010. TOPS 030. VIS 3-5SM BR. 14-16Z
BECMG AGL SCT030. 19Z AGL SCT050.
OTLK…VFR
OK
PNDLAND NW…AGL SCT030 SCT-BKN100.
TOPS FL200.
15Z AGL SCT040 SCT100. AFT 20Z SCT TSRA DVLPG..
FEW POSS SEV. CB TOPS FL450.
OTLK…VFR
Explanation:
In south central and southeastern Texas, there is a scattered
to broken layer of clouds from 1,000 feet AGL with tops at
3,000 feet, visibility is 3 to 5 SM in mist. Between 1400Z and
1600Z, the cloud bases are expected to increase to 3,000 feet
AGL. After 1900Z, the cloud bases are expected to continue
to increase to 5,000 feet AGL and the outlook is VFR.
In northwestern Oklahoma and panhandle, the clouds are
scattered at 3,000 feet with another scattered to broken layer
at 10,000 feet AGL, with the tops at 20,000 feet. At 1500
Z, the lowest cloud base is expected to increase to 4,000
feet AGL with a scattered layer at 10,000 feet AGL. After
Area Forecasts (FA)
The FA gives a picture of clouds, general weather conditions,
and visual meteorological conditions (VMC) expected over
a large area encompassing several states. There are six areas
for which area forecasts are published in the contiguous 48
states. Area forecasts are issued three times a day and are
valid for 18 hours. This type of forecast gives information
vital to en route operations, as well as forecast information
for smaller airports that do not have terminal forecasts.
Area forecasts are typically disseminated in four sections and
include the following information:
1. Header—gives the location identifier of the source of
the FA, the date and time of issuance, the valid forecast
time, and the area of coverage.
Example:
DFWC FA 120945
SYNOPSIS AND VFR CLDS/WX
SYNOPSIS VALID UNTIL 130400
CLDS/WX VALID UNTIL 122200…OTLK VALID
122200-130400
OK TX AR LA MS AL AND CSTL WTRS
Explanation:
The area forecast shows information given by Dallas Fort
Worth, for the region of Oklahoma, Texas, Arkansas,
Louisiana, Mississippi, and Alabama, as well as a portion
of the Gulf coastal waters. It was issued on the 12th day
of the month at 0945. The synopsis is valid from the time
of issuance until 0400 hours on the 13th. VFR clouds and
weather information on this area forecast are valid until 2200
hours on the 12th and the outlook is valid from 2200Z on the
12th to 0400Z on the 13th.
2. Precautionary statements—IFR conditions, mountain
obscurations, and thunderstorm hazards are described
in this section. Statements made here regarding height
are given in MSL, and if given otherwise, AGL or
ceiling (CIG) is noted.
Example:
SEE AIRMET SIERRA FOR IFR CONDS AND MTN
OBSCN.
TS IMPLY SEV OR GTR TURB SEV ICE LLWS AND
IFR CONDS.
NON MSL HGTS DENOTED BYAGL OR CIG.
Explanation:
The area forecast covers VFR clouds and weather, so the
precautionary statement warns that AIRMET Sierra should
be referenced for IFR conditions and mountain obscuration.
The code TS indicates the possibility of thunderstorms