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Reading METAR Weather
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Contents
Acronymese; ...METAR; ...Hourly METAR lists; Qualifiers; ...Sky Cover; ...Forecasts; ...Special Notes; ...METAR Sequence; ...METAR Sequence Another Way; ...ASOS/AWOS; ...Demo Sequences; METAR Terms Revisited; International METAR; ...Local METAR Conditions; ...

Acronymese
Is the LOA (A.K.A. Language of Aviation)
Worse yet, do you find yourself talking with fellow flyers and telling about the crazy day you had with ATC at MOD and getting the ATIS. You used an AWOS and also a TRACON for your ILS down to DH. The FAA submitted NPRM that meant you should tell you're A&P the new AD may be needed before the next TBO.

We pilots live and work in field that is inundated with acronyms. The advent of the computer required that all the historical names of airway intersections turned conventional spellings into five letter acronyms many of which are inevitable tongue twisters. Learning to read without vowels has come to include the ability to speak entire sentences using just letters. The weather has thousands of these that can substantially reduce speaking or typing time. Wouldn't you rather say CAVU instead of "ceiling and visibility unlimited?"

Some acronyms have become words over time because their meanings are universally understood in aviation. We say ATP when we mean airline pilot. We ask the A & P about the TBO coming up. Many of the acronyms used in our flying life are so specific to aviation that they aren't readily understood without explanation. Usually the very first question asked by a new flyer is the meaning of some acronym.
I have had occasion to be present when two unacquainted technicians in the computer technology industry met for the first time. It took just a few moments for them to test each other out through the use of acronyms before they agreed they both spoke the 'language' and could converse as equals. As pilots we often do the same when the conversation turns to flying. Pilots who delve deeper into the internet, electronics, weather, navigation and bureaucracy soon find that aviation becomes a melting pot of fields, each with their own dialect of acronymese.
I have included on my website many of the acronyms from METAR and TAF weather sources. I have never seen a purely aviation listing. I do know of lists with all the airway intersections, airports, and VORs.

METAR
--Letter K is U.S. ICAO country code that precedes location identifier.
--Metar began in late '60 and used worldwide and by military.
--METAR means Aviation Routine Weather Report
--TAF means Terminal Aerodrome Forecast.
--METAR is a Surface Report that lists surface winds, visibility in statute miles, weather and sky cover.
--BR means that visibility will exceed 5/8 mile
--FG means visiblity below 5/8 mile.

Time group starts with day followed by actual observation time in UTC. A METAR can be either routine or SPECI(AL. METARs exclude trend forecasts. COR is used for making a correction in a report.

Hourly METARs lists
Winds

Wind is five digits. Wind direction relative to true north is first three digits. Next is wind speed in knots. 100kt+ winds have three digits. VRB will indicate variable headings or velocity. Calm is 0000KT. METAR winds are all 'true' except when a ASOS or AWOS voice report. TAF winds are 'true'. Even Center winds are 'true'.

Visibility
--Runway visual range (RVR)
--Present weather
--Sky condition

Ceilings will not be stated as such. METAR Ceilings are based upon whether the layer of clouds are given as broken or overcast. Clear (CLR) exists only with ASOS and AWOS and even then only up to l2,000'. Pilot must infer from first layer of broken or overcast.

Temperature
All temperatures are given in Celsius.
--Dew point
Temp and dew point are reported in Celsius degrees using two digits. M is prefix for below zero numbers.
-- Altimeter setting (pressure)
Altimeter setting prefixed with A given in inches of mercury.
REMARKS.
Remarks begins with RMK divided into automated section and human section.

AUTO is by Automated Surface Observing System (ASOS) or Automated Weather Observing System (AWOS). ASOS are NWS operated often with state financing. AWOS is airport facility required by FAA. ASOS and AWOS reports visibility at one point. If automated visibility is below 1/4 mile the letter M precedes the visibility

ASOS/AWOS
993 placed 464 commissioned. CCR's has been there for a year but cannot be certified as accurate.
Ceiling-sky condition-visibility-temperature-altimeter-wind (true)-density.
ASOS also can give type of prepcipitation, and variable conditions
Report can be very deceptive because of being limited over time and averages.

Qualifiers:
Qualifiers state intensity or describe weather
Qualifiers description
- light MI shallow
BL blowing
VC vicinity 5-10 miles PR partial
SH showers
BC patches
no-sign moderate TS thunderstorm
DR low drifting
+ heavy FZ freezing

Phenomena classified as precipitation, obscuration or other. Precipitation described in order of dominance. Obscuration only if below seven miles.

Phenomena
Precipitation Obscuration
DZ drizzle BR Mist 5/8 visibility
IC ice crystals DU dust
UP precipitation unknown FG fog low visibility
RA Rain SA sand
IP ice pellets FU smoke
SN snow HZ haze
GR hail VA volcanic ash
GS Small hail/snow PY spray
VV obscured
Other
PO Dust devils
DS dust storm
SQ squalls
FC funnel cloud
+FC tornado
SS Sand storm

Sky condition is gives as cloud layers according to height. Sky-cover codes are clear, few, scattered, broken or overcast. Maximum of six layers. AWOS only three layers. No thin or partial reported in METAR

Sky cover
VV vertical visibility 8/8
SKC or CLR clear 0
FEW few 0 to 2/8
SCT scattered 3/8 to 4/8
BKN broken 5/8 to 7/8
OVC overcast 8/8

Forecasts
TW.........Surface Observation 3-hour trend
TAF........Terminal forecast
FD.........Winds Aloft Forecast
UA.........Pilot Reports
SD.........Radar Summaries
FDC........FDC NOTAMS (Facilities)
NO.........NOTAMs-Distant
FA.........Area Forecasts
The Area Forecast is best considered a 'dress rehearsal' in preparation for the big event.
WS.........SIGMETS
Warn all pilots of any weather up to 3000 square miles containing thunderstorms, icing, turbulence, or storms. Valid for four hours and named from November to Yankee except for Sierra and Tango which are reserved for warnings. SIGMETS follow area Forecast format.
WA.........AIRMETS
Conditions dangerous to small aircraft. Every six hours with six-hour outlook for moderate icing, turbulence, winds to 30 kts, less than 3 and ceilings below 1000'. Tango for turbulence, Zulu for icing
WW-A.......Amended Severe Weather Forecasts
CWA........Center Weather Advisories
Conditions within two hours including real time PIREPs.
WST........Convective SIGMETS
Actual and forecast thunderstorms and level four or higher storms covering 40% of area. Numbered and lettered in sequence and area. NONE if no SIGMET 24,795 in 1996.
ATC........Flow Control Advisories
WH.........Hurricane and Tropical Depressions
AWW........Severe Weather Forecast Alerts
AC.........Severe Weather Convective Outlook
A 24-hour perspective on thunderstorms less than severe.
10% is 'high' probability but when? Twice daily at 700Z and 1500Z valid for 24 hours. Goes with chart issued at 0800Z.
WW.........Severe Weather Warnings (Bulletin)

Every weather briefing must, according to the FAA, begin with an adverse weather advisory if such weather exists. There are several levels of such advisories. WHs are Hurricane Advisories, A Severe Weather Watch comes as a Bulletin called WW and as an Alert as AWW. The AWW is an advance notice for an area of severe thunderstorms with winds of 50+ knots and 3/4 inch hail.

TSNO........At the end of a weather observation to say that the station has no way to detect thunderstorms.
VNR.........VFR not recommended. Advisory appended to other items.

Special Notes
PE for ice pellets is being changed to PL to avoid a word when prefixed with RA for rain.
All VFR visibilities and cloud clearances are listed in FAR 91.155

METAR Sequence
When or SPECI (special weather report) sometimes data is omitted user must know and recognize sequence. Exceptions are RVR (runway visibility range) and SLP (sea level pressure) SPECI remarks will be in plain language.
1. wind information
2. prevailing visibility in statute miles
3. RVR information
4. Cloud layers and description as (FEW, SCT, BKN, OVC) with heights in three digits.
5. temperature and dewpoint in Celsius
6. Altimeter settings are begun with A or Q plus four digits
A2992 means given in inches and hundredths of mercury
Q1013 means hecto Pascals or centimeters of mercury

--RMK begins the remarks section which will include the sea level pressure
-- Always read in the past tense

METAR Sequence Another Way
----where
K first letter of all U. S. three letter identifiers making four letters. Alaska begins with PA, Hawaii with PH
-- when
First METAR time is six digits followed by Z. First two digits are day of month, last four are time of observation. All other times are four digits read in groups of two. From (or between) xx to xx.
----wind
First three digits are wind direction to nearer 10-degrees;. Next digits are wind speed usually in KT (knots) V between wind directions that vary more than 60-degrees and greater than 6 knots. VRB (variable) when less than 6 knots. Peak winds in remarks section with /time past hour of occurrence.
----Visibility
Fractions shown by /.SM (statute miles) follows.
Visual range uses R+runway/hundreds of feet. Letters other than R may be M(below sensor ability) P (above sensor ability) V (variable).
---- Weather
Two letter descriptor followed by two character weather type. Intensity - = light, none = moderate, + = heavy.
---- Clouds
Categorized on eights of the sky. (octas)
SKC = sky clear; FEW 1-2/8; SCT 3-4/8; BKN 5-7/8; PVC 8/8.
VV = vertical visibility; VV/// = indefinite ceiling
----Temperature/dewpoint
Listed in Celsius with / between. M = minus temperatures
---- Altimeter
A2992 if in inches. Q if metric.

ASOS/AWOS
AUTO included unless human makes remarks. Remarks tells number of sensors. CLR means no clouds below 12K.
--Usually from airports
--Hourly at 50 minutes after hour
--Specials preceded by S
--Reports (METAR) whenever visibility is less than 6 miles.
--ASOS will more than double weather reporting sites
--ASOS measures weather at touchdown zones
--ASOS detects hourly changes and sends them to weather network
--ASOS weather is available by phone and radio
--ASOS issues special report if visibility is below three miles
--

Demo Sequences
OSM FG VV000
visibility, zero statuted miles; fog; vertical visibility, zero
Demo Sequence
KOAK 091720Z 1818 22020KT 4 SM -SHRA BKN020CB
Interpretation
Oakland, 9th day of month made at 1720 valid 1800 9th to 1800 10th Winds are as 220 degrees at 20KT as direction and velocity, variable winds given as 180V220 or as VRB08 Visibility given as 4 miles prevailing. If greater than 6 miles gives as P6S(statute) Weather given as light showers (-SH) and rain (RA)
Clouds are broken (BKN) at 2000' (020) and cumulonimbus.

KPHL 1550Z 24007KT 7SM BKN009 OVC020 18/16 A3005
Interpretation
Philadelphia, PA 1550Z observation winds 270 degrees at 7 knots, visibility 7 statute miles, the ceiling is 900 broken with an overcast cloud deck at 2000 feet, temperature is 18 degrees centigrade, dew point 16 degrees centigrade, altimeter 30.05 inches

KLAX 1550Z 21008KT 1/2SM R14/3500V5500FT FG OVC 003 14/14 A3018
Interpretation
Los Angeles, CA 1550Z observation, winds 210 degrees at 8 knots, visibility 1/2 mile (statute), runway 14 runway visual range (RVR) is 3500 feet variable to 5500 feet in fog. The ceiling is 300 feet overcast,
temperature 14 degrees centigrade, dew point 14 degrees centigrade, altimeter 30.18

KACY 1545Z 00000KT 11/4SM -SHSN BKNOO6 OVC010 MO3/M03 A2942 RMK SB30
Interpretation
Atlantic City, NJ 1545Z observation, winds calm, visibility 1 and 1/4 statute miles in light snow showers, the ceiling is 600 feet broken with an overcast cloud deck at 1000 feet, temperature is minus 3 degrees centigrade, dewpoint is minus 3 degrees centigrade, the altimeter is 29.42, and remarks indicate that the snow began falling at 1530Z.

KBUF 1549Z 35015G27KT 1/4SM BLSN R31/1200FT VV003 01/M01 A3OI3
Interpretation
Buffalo, NY 1549Z Observation, winds are 330 degrees at 15 knots gusting to 27 knots with 1/4 mile )statute) visibility, runway 31 runway visual Range (RVR) is only 1200 feet, and the ceiling is indefinite 300 feet,
temperature is 1 degree centigrade, dew point is minus 1 degree centigrade and the altimeter is 30.13

KBOS 1549Z 15012KT6SM -RASN SCT004 BKN009 VOC015 02/M01 A2949 RMK PRESFR
Interpretation
Boston, Mass. 1549Z observation, winds from 150 degrees at 12 knots, visibility 6 statute miles in mixed light rain and snow, scattered clouds at 400 feet, a broken ceiling at 900 feet and an overcast deck at 1500 feet, temperature is 2 degrees centigrade, dewpoint is minimum 1 degree centigrade, the altimeter is 29.49 and
remarks indicate that the pressure is falling rapidly.

KBWI 1550Z S09008KT 3/4SM R10/3800FT -FZDZ PE 008OVC M01/M01 A2992
Interpretation
Baltimore, MD 1550Z Observation, winds directly out of the East (090 degrees) at 8 knots, with only 3/4's of a statute miles visibility, runway 10 has a runway visual range (RVR) of only 3800 feet in light freezing drizzle and ice pellets, with a ceiling of only 800 feet, temperature is minus 1 degree centigrade, a dew point of minus 1 degree centigrade and the altimeter is 29.90

METAR HIAD 081055 A 21019G27KT 1/2SM RO4/3000FT-SN BR SCT011 OVC015 O1/O3 A2945 RMK SLP045
Interpretation
METAR - hourly report
HIAD - ICAO location indicator
081055 - Issuance time:" ALL times in UTC as a two digit date and a four digit time.
A - ??
21019G27KT - three digit true north direction, nearest 10 degrees or VRB (variable); gusts to 27 knots.
1/2SM prevailing visibility in statute miles
R04/3000FT - runway number and visual range in feet
-SN BR - Light snow and mist (French)
SCT 011 - Scattered clouds at 1100'
OVC015 - Overcast 1500'
temperature 1° Celsius, dewpoint 3° Celsius
A2945 - Altimeter 29.45 inches of barometric pressure
RMK - remarks SLP045 - Sea level pressure 3045

KPHL 1550z 24007KT 7SM BKN009 OVC020 18/16 A3005
Interpretation
Philadelphia, PA 1550Z observation. Winds 240 degrees at 7 knots, visibility 7 statute miles, the ceiling is 900 feet broken with an overcast cloud deck at 2000 feet, temperature 18 degrees centigrade, dewpoint 16 degrees centigrade, altimeter 30.05 inches of mercury.

KLAX 1550Z 21008KT 1/2SM R14/3500V5500FT FG OVC003 14/14 A3018
Interpretation
Los Angeles, CA 1550Z observation, winds 210 degrees at 8 knots, visibility 1/2 statute mile, runway 14 runway visual range (RVR) is 3500 feet variable to 5500 feet in fog, the ceiling is 300 feet overcast, temperature is 14 degrees centigrade, dewpoint 14 degrees centigrade, altimeter 30.18 inches of mercury.

KACY 1545z 00000KT 11/4SM -SHSN BKN005 OVC010 M03/MO3 A2942 RMK SB30
Interpretation
Atlantic City, NJ 1545Z observation, winds calm, visibility 1 1/4 statute miles in light snow showers, the ceiling is 600 feet broken with an overcast cloud deck at 1000 feet, temperature is minus 3 degrees centigrade, dewpoint is minus 3 degrees centigrade, the altimeter is 29.42 inches of mercury, and remarks indicate that the snow began falling at 1530Z.

KBUF 1549z 35015G27KT 1/4SM BLSN R31/1200FT VV003 01/MO1 A3013
Interpretation
Buffalo, NY 1549Z observation, winds are 350 degrees at 15 knots gusting to 27 knots with 1/4 statute mile visibility in blowing snow, runway 31 runway visual range (RVR) is only 1200 feet, and the ceiling is indefinite 300 feet, temperature is 1 edge centigrade, dewpoint is minus 1 degree centigrade, and the altimeter is 30.13 inches of mercury.

KBOS 1549z 15012KT 6SM -RASN SCT004 BKN009 OVC015 02/M01 A29.49 RMK PRESFR
Interpretation
Boston, Mass 1549Z observation, wind from 150 degrees at 12 knots, visibility 6 statute miles in mixed light rain and snow, scattered clouds at 400 feet, a broken ceiling at 900 feet and an overcast deck at 1500 feet, temperature is 2 degrees centigrade, dewpoint is minus 1 degree centigrade, the altimeter is 29.49 inches of mercury and remarks indicate that the pressure is falling rapidly.

KBWI 1550Z 09008KT 3/4SM R10/3800FT -FZDZ PE OO80OVC M01/M01 A2990
Interpretation
Baltimore, MD 1550Z observation, winds directly out of the east at 8 knots, with only 3/4 statute mile visibility, runway 10 has a runway visual range of only 3800 feet in light freezing drizzle and ice pellets, with a ceiling of only 800 feet, temperature is minus 1 degree centigrade, a dew point of minus one degree centigrade and an altimeter setting of 29.90 inches of mercury.

KLAX 231850Z VRB03KT 10SM FEW023 BKN030 BKN050 11/05
A2984 RMK AO2 SLP102 T01060050
Interpretation
A2984 - Altimeter setting is 29.84 "Hg
RMK - Remarks
A02 means that the site is automated and has a precipitation sensor. If it were AO1, there would be no
precip sensor
SLP 102 - Sea level Pressure is 1010.2 hP (millibars)
T01060050 - Hourly Temperature and Dewpoint
T - Temp
0 after T signifies next three digits are temp above zero Celsius (1=below zero)
106 - temp is positive 10.6 degrees C
0 after 106 signifies next three digits are dewpoint above zero Celsius (1=below zero)
050 = dewpoint is positive 5.0 degrees C

METAR Terms Revisited
--Missing data will screw up the weather sequence. You must learn the sequence to notice this.
--Exceptions to missing data omission occur such as RVRNO OR SLPNO
--Data sequence is always 3Ws;
--Where
KOAK with K for United States plus three letter identifier
--When
23 as day of the month
1345Z as time
Written as 231345Z
--Wind
230 always as three digit TRUE direction. V used when direction varies over 60 degrees
25 two digit wind velocity
G30KT gusts and velocity and units
Five zeros for calm winds
PK WND 22025/15 means peak gust of 25 occurred 15 minutes past the hour
--Visibility
3/4 fractions of statute mile
M0600FT --M means below sensor's ability to measure
P6000FT --P means above sensor's ability to measure
R --in front gives runway number and
L-C-R --gives runway location references to other runways
--Clouds
SKC -- sky clear
FEW -- >2 2 eights clouds
SCT -- 4 eights clouds
BKN -- 7 eights clouds
OVC -- eight eights clouds
Temperature/dew point
M -- minus
15/13
Altimeter
A --mean setting in inches
Four digits in inches and hundredths. Decimal point omitted.

ASOS.AWOS METAR
--Identified by AO1 or AO2
--Only fully automated site will say AUTO
--CLR means no clouds below 12,000
SPECI -- special report
COR -- correction
AUTO -- automated observation
VRB -- when wind direction is variable below 6 knots
RMK -- when velocity over 25 knots
OVC -- Overcast
TCU -- towering cumulus
CB -- cumulonimbus
VV -- vertical visibility occasionally variable visibility
SLP -- Sea level pressure
TO -- T means temperature and O means positive
T1 -- T means temperature and 1 means minus
NSW --no significant weather
UP --unknown precipitation in automated observations
BC -- patches
PR -- partial
VC -- vicinity
S -- wind shear

International METAR
Can some tell me what the '7000' represents?

YPLM 130750Z 24009KT 7000 VCSH FEW030TCU SCT050 BKN080 22/21 Q1016

Weather at YPLM at 0750 Zulu on the 13th of the month:
Winds - 9 kts at 240 degrees
Visibility - 7000 meters
Showers in the vicinity
Clouds - Few at 3000 feet with towering cumulus, Scattered at 5000, Broken at 8000
Temp - 22 degrees C
Dew Point - 21 degrees C
Altimeter - 1016mb? Not sure, never used millibars before.

Local METAR Conditions
I wrote this little proggy to get the local conditions at my airport quickly. I thought some you might be interested in checking it out. It's a little rough but I thought if you guys are game, it would be
nice to have some feedback. It's free. No commercial aspirations....
http://www.unconventional-wisdom.org/Software/MetarMonkey.asp
Jim


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