Prepared by: Troy M. Kimmel, Jr.
Lecturer, Studies in Weather and Climate
Manager, Weather and Climate Resource Center
Department of Geography, University of Texas at Austin
Certificate Holder, National Weather Service Certificate of Authority to
Take Weather Observations
A METAR is the Aviation Routine Weather Observation created at thousands of locations (primarily, airports) around the world every hour. It provides insight on a number of weather elements being observed at the airport or observing location. Each observing location is unique in what is reported... the largest airports report all types of automated and humanly augmented data... while smaller locations may be completely automated and don't include any humanly augmented information.
Here is an example of a METAR:
KAUS 092135Z 26018G25KT 8SM -TSRA BR SCT045CB BKN060 OVC080 30/21 A2992 RMK FQT LTGICCCCG OHD-W MOVG E RAB25 TSB32 CB ALQDS SLP132 P0035 T03020210 =
So what does this METAR tell us?
KAUS - Austin Bergstrom International Airport
092135Z - Date/Time Group. "09" is the day of month... "2135Z" is Greenwich time or 3:35 pm CT
26018G25KT - Wind Group. Direction is "260 degrees"
(west wind)... at 18 gusting to 25 knots (multiply by
1.15 to get speed in miles per hour)
8SM - Visibility (8 statute miles)
-TSRA BR - Current Weather type/Obscurations
to Visibility... In this case, thunderstorm and light rain... mist
Some other commonly used abbreviations:
FG (Fog)
GR (Hail)
SN (Snow)
FZRA (Freezing Rain) FZDZ (Freezing Drizzle)
RA (Rain)
TS (T'Storm, no rain) PL (Ice Pellets)
DZ (Drizzle)
VCTS (T'Storm in the Vicinity)
SCT045CB BKN060 OVC080 - Cloud bases/types ...
cloud coverage is based on Octas (8ths of sky)
There is a scattered layer of clouds, in fact, cumulonimbus clouds, that
are covering 2/10-4/10ths of the sky
with bases at 4,500 feet AGL. Other cloud bases are at 6,000 and 8,000
feet AGL that, when cumultatively
added to underlying cloud layers, ccreate broken and then overcast layers.
30/21 - Air temperature/dewpoint temperature group
in whole degrees Celsius
In this case, air temperature is 30 degrees C... dewpoint temperature is
21 degrees C.
A2992 - Altimeter (pressure) reading in inches of mercury (29.92 in/hg)
RMK - Remarks section follows
FQT LTGICCCCG OHD-W MOVG E RAB25 TSB32 CB ALQDS
-
Thunderstorm/precipitation comments... there is frequent lightning (in
cloud, cloud-to-cloud, and
cloud-to-ground) overhead through the west... rain began at 25 minutes
after the hour... the thunderstorm
began at 32 minutes after the hour... there are cumulonimbus clouds visible
in all quadrants of the sky
SLP132 - Sea Level Pressure Reading in millibars
(to the tenths place)
You add a "9" or "10" before this number to get the number closest to 1000
mb
In this case.. the reading is equal to 1013.2 millibars
P0035 - Precipitation amount since the top of the
last hour in hundredths of an inch
In this case, 0.35" has fallen
T03020210 - Air Temperature/Dewpoint Temperature
Group (to tenths of a degree)
A degree of celsius is larger (by a factor of 1.8) than a degree of fahrenhiet.
As a result, we need to
have the air temperature/dewpoint temperatures to a tenth of degree (the
temperatures earlier in the
report are rounded). The temperature, depicted by the first four numbers
in this sequence
following the "T", is 30.2 degrees C, the dewpoint (depicted by the second
group of 4 numbers) is 21.0 C.
AN IN-DEPTH LOOK INTO
HOW TO DECODE AND INTERPRET
METAR DATA
Adapted from paper originally prepared by Larry Riddle,
Climate Research Division, Scripts Institute of Oceanography
Prepared by: Troy M. Kimmel, Jr.
Lecturer, Studies in Weather and Climate
Manager, Weather and Climate Resource Center
Department of Geography, University of Texas at Austin
Certificate Holder, National Weather Service Certificate of Authority to
Take Weather Observations
When we examine surface weather observations, better known as METARS (roughly translates from the French as Aviation Routine Weather Report), it is important that you understand that they represent the weather conditions that existed at one particular time at one specific location (usually an airport). Observed conditions may or may not be regional in scope. For example, a thunderstorm and rain shower reported at Austin Bergstrom International Airport does not necessarily mean that there is a thunderstorm and rain shower over other areas of Austin. Rainfall measurements during that same thunderstorm and rain shower at Austin Bergstrom International Airport simply means how much rain fell in a six inch diameter area (the rain gauge diameter) at Austin Bergstrom International Airport.
Routine weather observations are usually transmitted just before the top of the hour with special weather observations transmitted as certain established meteorological criteria are met.
EXAMPLES OF METARS
METARS can be as simple as...
KTVL 021553Z 02012KT 10SM SKC 15/05 A3000
...or as complex as...
KMWL 111155Z 13012KT 8SM -TSRA SCT100CB OVC250 08/06 A2998 RMK RAB32 OCNL LTGIC VC SW-OHD TSB34 MOV NE P0012 T00780059 SLP150 10105 20052 60012
A METAR primarily consists of four parts, the last of which (a remarks section) isn't always in the observation. Using this last more complex observation, let's take a look at each of these elements.
PART 1: Identification
KMWL 111255Z
KMWL
Observation taken at Mineral Wells, TX Airport
111155Z
Observation taken on the 11th day of the month (first
two digits) and at 1155 Universal Coordinated Time (time along the Greenwich
Meridian); also called "Zulu" time.. thus the "Z."
How you do you tell local time?
In order to calculate local time for the observation,
you must know how many time zones you are away from the Greenwich Meridian.
Here in central Texas, we are in the Central Time zone, or six time zones
away from the Greenwich Meridian. Accordingly, you should subtract 6 hours
from the time on the METARS to get local time during standard time; you
should subtract 5 hours from the posted time when we are observing daylight
savings time. Assuming this observation was during December (during CST),
we subtract 6 hours to get a local time in Mineral Wells of 5:55 a.m.
PART 2: Observation
13012KT 8SM -TSRA SCT100CB OVC250
13012KT
Wind Speed and Direction
Add a zero to the first two numbers (13) to come up with
130. This tells us that the winds are blowing from 130 degrees from true
north (130 degrees degrees clockwise from true north).
The last three numbers tells us wind speed in knots..
in this case 12 knots. If there had been wind gusts to 25 knots, the observation
would have read "13012G25KT."
FYI.. In order to convert winds to mph, remember that
1 knot equals 1.15 mph.
8SM
Visibility in statute miles (SM). Any visibility less
than seven (7) miles must have a weather type following it to denote
what is reducing the visibility.
The visibility may be followed by something like R28L/2000ft.
This is what we call a "runway visual range" (runway visibility) observation.
The RVR reading above says "runway 28L visibility is 2000 feet. M2000 says
"less than 2000" (M stands for minus) and P2000 says "greater than 2000
feet" (P stands for plus).
-TSRA
Current weather (if there is any)
This stands for a thunderstorm (TS) and light (the -
that preceeds the weather type) rain.
Here is a list of weather descriptors that you will see used in this current weather section...
Intensity: -
Light Intensity
Moderate Intensity (no symbol)
+ Heavy Intensity
VC In the Vicinity
Descriptor: MI Shallow
PR Partial
BC Patches
DR Low Drifting
BL Blowing SH Showers
TS Thunderstorm FZ Freezing
VCTS Thunderstorm in the Vicinity
Precipitation: RA Rain
DZ Drizzle
SN Snow
SG Snow Grains
IC Ice Crystals PL
Ice Pellets (Sleet) GR Hail
GS Small Hail/Snow Grains
UP Unknown Precipitation
Obscuration: FG Fog (less than 5/8 mi
visibility)
BR Mist (fog with 5/8 to 7 mi visibility)
HZ Haze
FU Smoke
DU Widespread Dust
SA Sand
PY Spray (sea)
VA Volcanic Ash
Others: SQ Squall
DS Duststorm
SS Sandstorm
PO Well Developed Dust/Sand Whirls
FC Funnel Cloud
+FC Tornado
SCT100CB OVC250
Cloud coverage and type as well as height of base.
The clouds over Mineral Wells are in two observable layers
at the time of this observation. The first layer is a "scattered" layer
with its bases at 10,000 feet AGL (you add two zeros to the numbers shown..
100 becomes 10,000 feet) with the second layer being an "overcast" layer
at 25,000 feet (250 becomes 25,000).
The "CB" that follows the first cloud group.. the one
with bases at 10,000 feet AGL.. denotes that this is a cumulonimbus (thunderstorm)
cloud.
Here is how we define the cloud coverage in METAR observations:
SKC
No clouds (manual weather station)
CLR
No clouds below 12,000 feet (automated ASOS/AWOS stations)
FEW
Few Clouds (1/8 to 2/8 of the sky is covered with clouds)
SCT
Scattered Clouds (3/8 to 4/8 of the sky is covered with clouds)
BKN
Broken Clouds (5/8 to 7/8 of the sky is covered with clouds)
OVC
Overcast Clouds (8/8 or all of the sky is covered with clouds)
Here is simple table of cloud types (code numbers are sometimes used in remarks section):
Low
Middle
High
Code
Cloud Type
Cloud Type
Cloud Type
0 No Clouds Present No Clouds Present No Clouds Present
1
Cu (Fair Weather) As (Thin,Sun
vsbl)
Ci (Filaments,strands)
2
Cu (Towering/TCU) As (Thick,no Sun)
Ci (Dense)
3
Cb (No Anvil vsbl) Ac (Thin;semitransparent)
Ci (often left over from Cb)
4
Sc (from Cu)
Ac (Patchy)
Ci (Hooks/Filaments thickening)
5
Sc (not from Cu)
Ac (Thickening)
Ci/Cs (low on horizon;<45deg)
6
St (in sheet/layer)
Ac (from Cu,Cb)
Ci/Cs (high in sky>45deg)
7
CuFr/StFr (Bad Wx) Ac (Ac w/As,Ns)
Cs (covering entire sky)
8
Cu and Cs
Ac (w/turrets)
Cs (not covering entire sky)
9
Cb (w/Anvil)
Ac (Chaotic)
Cc alone and/or Ci and Cs
Abbreviations used:
Ac - Altocumulus
As - Altostratus
Cb - Cumulonimbus
Cc - Cirrocumulus
Ci - Cirrus
Cs - Cirrostratus
Cu - Cumulus
StFr - Stratus Fractus
CuFr - Cumulus Fractus Ns - Nimbostratus
Sc - Stratocumulus
St - Stratus
TCU - Towering Cumulus (Cumulus Congestus)
Wx - Weather
PART 3: Instrument Readings
08/06 A2998
08
This is the air temperature in celsius (whole/rounded
degrees)
06
This is the dew point temperature in celsius (whole/rounded
degrees)
A2998
The altimeter setting (a measure of barometric pressure)
is 29.98 inches of mercury (corrected to sea level)
PART 4: Remarks and Coded Section
RMK RAB32 OCNL LTGIC VC SW-OHD TSB34 MOV NE P0012
T00780059 SLP150 10105 20052 60012
This remarks section (denoted by the code RMK) varies weather observing station to weather observing station. Some stations report remarks data in great details, other don't. We will only address what we're seeing in the Mineral Wells observation. For a complete detailed listing of all possible remarks, see pages 25-29.
RAB32
Rain began at 32 minutes after the hour; in this case,
at 1132Z
OCNL LTGIC VC SW-OHD
Occasional lightning in cloud in the vicinity of the
weather observing station southwest through overhead
TSB34 MOV NE
The thunderstorm (audible thunder) began at 34 minutes
after the hour; in this case, at 1134Z... and is moving northeastward
P0012
Precipitation since last hourly observation; in this
case, 0.12 inch
T00780059
Air and Dew Point Temperature Celsius (in tenths of degrees)
First series of four numbers is air temperature... 7.8
degrees Celsius
Second series of four numbers is dew point temperature...
5.9 degrees Celsius
Note that these numbers, after rounding, are found in
the instrument readings section above.
If either air or dew point temperature are below 0 degrees
C, then the first number in the
four number series will become "1" instead of "0."
For example, T10501105 indicates
an air temperature of -5.0 degrees Celsius and a dew
point temperature of -10.5 degrees Celsius.
SLP150 Sea Level Pressure (another way to express atmospheric
pressure)
In this case is 1015.0 millibars (The last numbers is
to the right of the decimal point.. a indication of tenths). You always
prefix the numbers shown following the "SLP" with a "9" or a "10".. using
the number that brings the total number closest to 1000.
Example: SLP025 equals 1002.5 millibars, SLP997 equals
999.7 millibars
10105 Maximum temperature over the last 6 hours is 10.5 degrees Celsius
20052 Minimum temperature over the last 6 hours is 5.2 degrees Celsius
60012 Precipitation recorded in the previous 6 hour
period is 0.12 inch
METAR WEATHER OBSERVATIONS --
Manual/Augmented Comments
Revised December 1999
Original April 1998
Prepared by: Troy M. Kimmel, Jr.
Lecturer, Studies in Weather and Climate
Manager, Weather and Climate Resource Center
Department of Geography, University of Texas at Austin
Certificate Holder, National Weather Service Certificate of Authority to
Take Weather Observations
Manual or augmented comments in METAR weather observations are found toward the end of the observation in the "RMK' section.
Within these observations, you will find a number of abbreviations
that have very specific meanings.
For example, location descriptions are specific:
AP - Airport - At Airport location
VC - Vicinity - Within 5 to 10 miles of the station (usual
point of observation).. but not at the station
DSNT - Distant - More than 10 miles away from the station
(usual point of observation)
ALQDS - All Quadrants
Let's now look at the proper order of the comments in the "RMK" section, per the National Weather Service and Federal Aviation Administration guidelines:
After the "RMK" abbreviation:
- A01/A02 (if present) indicate, at least, a partially
automated observation
A01 - Automated weather equipment without a precipitation
type descriminator
A02 - Automated weather equipment with a precipitation
type descriminator
- +FC (tornado), FC (funnel cloud) location, beginning
and ending time
TORNADO B34 VC STN NW MOV NE - Tornado began
34 minutes after the hour in the vicinity station northwest
moving northeast
FUNNEL CLOUD B34E39 - Funnel cloud began
at 34 minutes after the hour.. ended at 39 after the hour..
- PKWND (peak wind) data
PK WND 33026/1429 - Peak wind from 330 degrees
at 26 knots at 1429Z
- WSHFT (wind shift)/FROPA (frontal passage) time
WSHFT34 - Wind shift at 34 minutes
after the hour
WSHFT FROPA34 - Wind shift with frontal
passage at 34 minutes after the hour (manual stations only)
- TWR (tower)/SFC (surface) visibility
TWR VIS 1 - Tower Visibility is one mile
SFC VIS 2 ½ - Surface Visibility
is one mile
- VIS (visibility) variability
VIS1V3 - Visibility variable between one
and three miles
- SECTOR VIS (sector visibility)
VIS N 3 - Visibility north is three
miles
- VISIBILITY AT SECOND SITE (Automated Stations Only)
VIS 2 RY36 - Visibility is two
miles at runway 36
- Precipitation not at station
SHRA VC S-SW - Rain showers vicinity
observing station south through southwest
- Lightning location and frequency
OCNL LTGIC DSNT N - Occasional lightning
in cloud distant north
FRQ LTGCCCG VC W - Frequent lightning
cloud to cloud and cloud to ground vicinity of the airport
observing station to the west
CONS LTGCWCA ALQDS - Continuous lightning
cloud to water and cloud to air all quadrants
CONS LTGCG AT AP - Considerable
lightning cloud to ground at airport
Note: Lightning frequency is
defined by the following terms:
OCNL - Occasional - Less than 1 flash per minute
FRQ - Frequent - About 1 to 6 flashes per minute
CONS - Continuous - More than 6 flashes per minute
Note: Lightning types are defined as follows:
CG - Cloud to Ground
IC - In cloud
CC - Cloud to cloud
CA - Cloud to Air
CW - Cloud to Water
- Precipitation beginning and ending
RAB05E30 - Rain began at 5 minutes
after the hour and ended at 30 minutes after the hour
SNB30 - Snow began at 30 minutes after
the hour
RAE45 - Rain ended at 45 minutes after
the hour
- Thunderstorm beginning and ending; location
TSB05E30B52 - Thunderstorm began at
05 minutes after the hour, ended at 30 minutes after the hour then
began again at 52 minutes after the hour
TSB12 - Thunderstorm ended at 12 minutes
after the hour
TS OVD MOV N - Thunderstorm is overhead
and moving northeastward
TS VC NE MOV NE - Thunderstorm is
in the vicinity northeast of the observing station and is moving northeastward
- GR (hail) size - over 1/4" in diameter (if below,
coded as GS - Snow Grains, Small Hail)
GR 3/4 - Hail diameter 3/4 inch
- Virga presence/location
VIRGA SW - Virga observed southwest
- Variable ceiling height
CIG 005V010 - Ceiling variable between
five hundred and one thousand feet
- Obscuration(s)
FG FEW000 - Fog obscuring 1/8
to 2/8ths of the sky
VA SCT000 - Volcanic ash obscuring
3/8 to 4/8ths of the sky
FU BKN020 - Broken layer (5/8
to 7/8ths of sky obscured) of smoke aloft based at 2,000 feet AGL
- Variable sky condition
SCT V BKN - Scattered variable broken
sky cover
BKN025 V OVC - The broken layer at
2,500 ft AGL is variable broken to overcast
- CB (cumulonimbus), TCU (towering cumulus), other clouds
location
TCU DSNT SE - Towering Cumulus (Cumulus
Congestus) distant southeast
CB DSNT N-NE - Cumulonimbus distant
north through northeast
ACC W - Altocumulus castellanus west
CCSL OVR MTNS E - Standing lenticular
cirrocumulus over mountains east of station
- CEILING AT SECOND SITE (Automated Stations Only)
CIG 020 RY36 - Ceiling of 2,000 feet
AGL at runway 36
- PRESFR (pressure falling rapidly), PRESRR (pressure rising rapidly)
- SLP (sea level pressure) in millibars - prefix the numbers
shown with a "9" or "10" which ever
brings the total number (the last
number is a tenths figure) closest to 1000.
Examples: SLP105 - 1010.5 millibars
SLP997 - 999.7 millibars
SLPNO - Sea level pressure not available or not reported at this location
- ACFT MSHP (aircraft mishap) - Not transmitted externally
- NOSPECI (no specials issued) - Only hourly observations issued from this station
- SNINCR (snow increase in depth)
SNOINCR 1/4 - Indicates
1 inch snow in last hour with 4 inches total snow on ground
- FIRST/LAST observation - when stations do not report 24 hours a day
- P0000 - Precipitation since last hourly observation
P0000 - A trace of rain (less than
0.01 inch)
P0034 - 0.34 inch of rain
P0565 - 5.65 inches of rain
- 60000 - 3 or 6 hourly precipitation (00Z,06Z,12Z,18Z
obs have 6 hourly obs/03Z,09Z,15Z,21Z obs have 3 hourly rainfall)
60000 - A trace of rain (less than
0.01 inch)
60059 - 0.59 inch of rain
- 70000 (12Z obs only) - 24 hour precipitation
70000 - A trace of rain (less than
0.01 inch)
70001 - 0.01 inch of rain
71245 - 12.45 inches of rain
- 4/--- Snow depth on ground
4/001 - One inch of snow on the ground
4/025 - Twenty five inches of snow
on the ground
- 933--- Water equivalent of snow
933036 - Water equilavent of snow
is 3.6 inches
- 8/LMH Cloud types (low, middle, high clouds)
(See supplemental text page 22 for
code numbers used for high/middle/low clouds)
8/6// - Lower level clouds are stratus
in sheets/layers; the / in the mid and high level cloud positions tells
us that the low
clouds are overcast preventing the observer from identifying any mid and
high level cloud types.
8/004 - No clouds in low and middle
levels; Cirrus hooks and filaments noted as high cloud type.
8/100 - Fair weather cumulus clouds
in low clouds, no clouds above
-9/LMH Cloud cumulative coverage (low, middle,
high clouds) - Military stations ONLY
9/700 - Low clouds cover 7/8ths
of the sky, no mid and high level clouds
9/8// - Low clouds cover 8/8ths
of the sky; an overcast (not able to determine mid/high clouds
9/138 - Low clouds cover 1/8ths
of the sky, when added to the middle clouds then 3/8ths of the sky is covered
and, finally, when added to the high clouds then 8/8ths of the sky is covered
(an overcast).
- Txxxxxxxx Air temperature/dew point temperature
(in tenths degrees C)
T02040015 - first four numbers following
the "T" (0204) depicts air temperature in Celsius
in tenths of degrees (20.4 degrees C); the second four numbers (0015) depicts
dew point temperature in
Celsius in tenths of degrees (1.5 degrees C). When the air or dew point
temperature is a negative number,
the first digit of each series will be "1" instead of "0"; Example: T10241040
= air temperature is -2.4C,
dew point temp is -4.0C.
- 10000 6 hour maximum air temperature
10326 is 32.6 degrees Celsius
11005 is -0.5 degrees Celsius
- 20000 6 hour minimum air temperature
20015 is 1.5 degrees Celsius
21040 is -4.0 degrees Celsius
- 4xxxxxxxx (06Z ob only) Previous calendar
day 24 hour maximum/minimum air temperature
401550035 - first four numbers following
the "4" tell you the calendar day maximum air temperature in tenths of
degrees
(15.5 degrees C) while the second group of four numbers give you the calendar
day minimum temperature
in tenths of degrees (3.5 degrees C).
When the maximum/minimum temperature is a negative number, the first digit
of each series will be "1"
instead of "0"; Example: 410241040 = maximum temperature is -2.4C, mimimum
temperature is -4.0C.
- 50000 3 hourly pressure change
(in millibars)
After the "5", the first number is a tendency
code where 0-3 depicts that the pressure is higher than it was 3 hours
ago,
0 and 4-5 depicts pressure is the same as
it was 3 hours ago and 5-8 depicts pressure lower than it was three hours
ago.
The last three numbers tells us the amount
of pressure change, in millibars, over the last 3 hours.
Examples: 56012 - Pressure is lower than
it was three hours ago; pressure change was 1.2 millibars.
51032 - Pressure is higher than three hours ago; pressure change is 3.2
millibars.
- RVRNO Runway visual range data not available
- PWINO Present weather data not available
- PNO Precipitation rain gauge data not available
- FZRANO Freezing rain sensor data not available
- TSNO Thunderstorm
data not available
04Jul00 tmk