Key to METAR Surface Weather Observations

Unedited Surface Weather Observations
(METAR/SPEC)
Latitude

41� 59'
Longitude

-87� 55'
Station
Elev. (ft)
658
Time
Conversion
Day

02
Mon.

01
Year

1999
SID

ORD
    WIND VISIBILITY          
T
Y
P
E
TIME
(LST)
DIR
TRUE
SPD
KTS
GUST
KTS
VARIABILITY TRUE SURFACE
STATUTE
MILES
RUNWAY
VISUAL
RANGE (FT)
PRESENT
WEATHER
SKY CONDITIONS TEMP
�C
DEW
POINT
�C
ALTI-
METER
INS.
1 2 3 4 5 6 7 8 9 10 11 12 13
S
0049
100
 21  
 
 
3/4
R14R/4000VP6000FT   
-SN BR    
BKN005 OVC015            
-08
-09
A3024
squiggly line
squiggly line
Station (Type, Name, State)

ASOS CHICAGO, IL
 
REMARKS AND SUPPLEMENTAL CODED DATA
14
PRESFR P0000 (CG)
Column
Number
1 TYPE Type of Observation S - routine (standard) hourly observation.
Non-standard time observation will also show type S on these forms, although they are not.
2 TIME(LST) Time of Observation reported as "Local Standard Time"
3 DIR TRUE Wind Direction direction from which wind blows. Reported to nearest degree, 0 to 359, from true north. Based on a 2-minute average just prior to observation time.
4 SPD KTS Wind Speed reported in knots. Based on a 2-minute average just prior to observation time.
5 GUST KTS Wind Gust maximum 5-second peak wind speed measured in the last ten minutes.
6 VARIABILITY TRUE Variable Wind Direction Indicator determined if during the 2-minute evaluation period it varies by 60 degrees or more regardless of wind speed.
7 SURFACE STATUTE MILES Prevailing Surface Visibility reported in statute miles & fractions. Max reported visibiltiy is 10 statute miles. Derived by sensors. Reported as variable is prevailing visibility varies by 1/2 mile or more and the average visibility is less than 3 miles.
8 RUNWAY VISUAL RANGE (FT) Secondary Visibility Measurements reported when surface visibility 1 mile or less. Runway Visual Range: R; 2-digit runway designator Left, Center, or Right as needed; "/index.html"; Minus or Plus, 4-digit value; 4-digit value Varialbility 4-digit value and tendency Down, Up or No change)
9 PRESENT WEATHER See Table of Significant Weather and Obscurations Reported by ASOS (below)
10 SKY CONDITION Cloud amount, height and type SKy Clear 0/8, FEW">"0/8-2/8, SCaTtered 3/8-4/8, BroKeN 5/8-7/8, OVerCast 8/8; 3-digit height in hundreds of ft; Towering CUmulus or CumulonimBus in METAR. Vertical Visibility for obscured sky and height "VV004". More than 1 layer may be reported. ASOS stations report only, CLeaR for "clear below 12,000 feet"
11 TEMP Dry Bulb Temperature reported in whole degrees Celsius
12 DEW POINT Dew Point Temperature reported in whole degrees Celsius
13 ALTIMETER (INS.) Altimeter Setting in Inches of Mercury reported to nearest hundreth of an inch. Altimeter setting is the computed pressure value to which an aircraft altimeter scale is set so that it will indicate the altitude above mean sea level of an aircraft on the ground at the location for which the value was determined.
14 REMARKS AND SUPP'L CODED DATA See table xxx below for details

Table of Significant Weather and Obscurations Reported under "Present Weather" Column

QUALIFIER: Intensity or Proximity
"-" Light "no sign" Moderate "+" Heavy
VC Vicinity: but not at aerodrome. Between 5 and 10SM of the point(s) of observation
Descriptor
MI Shallow BC Patches PR Partial TS Thunderstorm
BL Blowing SH Showers DR Drifting FZ Freezing
WEATHER PHENOMENA
Precipitation
DZ Drizzle RA Rain SN Snow SG Snow grains
IC Ice crystals PL Ice pellets GR Hail GS Small hail/snow pellets
UP Unknown precipitation in automated observations
Obscuration
BR Mist(>= 5/8SM) FG Fog(< 5/8SM) FU Smoke VA Volcanic Ash
SA Sand HZ Haze PY Spray DU Widespread dust
Other
SQ Squall SS Sandstorm DS Duststorm PO Well developed dust/sand whirls
FC Funnel cloud +FC tornado/waterspout

Table of Remarks and Supplemental Coded Data

The following groups are reported in the Remarks section of the SWO reports. Remarks include clarifying or augmenting data concerning elements in the body of the SWO reports, additive coded data, and maintenance data. If an element or phenomena does not occur, is missing, or cannot be observed, the corresponding group and space are omitted (body and/or remarks) from that particular report, except for Sea-level Pressure (SLPppp). SLPNO shall be reported in a METAR when the SLP is not available. The left most column are examples.
TORNADO, FUNNEL CLOUD or WATERSPOUT TORNADIC ACTIVITY Augmented; report should include TORNADO, FUNNEL CLOUD or WATERSPOUT, time (after the hour) of beginning/end, location, movement; e.g.,TORNADO B25 N MOVE E
AO2 TYPE OF AUTOMATED STATION AO1; automated station without a precipitation descriminator. AO2; automated station with precipitation descriminator.
PK WND 20032/25 PEAK WIND PK WND dddff(F)/(hh)mm; direction in tens of degrees, speed in whole knots, time (reported in UTC) in minutes after the hour. Only minutes after the hour is included if the hour can be inferred from the report.
WSHFT 1715 WIND SHIFT,/FONT> WSHFT followed by hours and minutes of occurrence. The term FROPA may be entered after the time if it is reasonably certain that the wind shift was a result of a frontal passage.
TWR VIS 2 TOWER OR SURFACE VISIBILITY TWR VIS vvvvv: visibility reported by tower personnel,e.g., TWR VIS 2; SFC VIS vvvvv: visibility reported by ASOS or observer.
VIS 3/4V1 1/2 VARIABLE PREVAILING VISIBILITY VIS vnvnvnvnvnVvxvxvx vxvx; reported if prevailing visibility is <3 statute miles and variable.
VIS 3/4 RWY11 VISIBILITY AT SECOND LOCATION VIS vvvvv(LOC); reported if different than the reported prevailing visibility in the body of the report.
FRQ LTG NE LIGHTNING (FREQUENCY) LTG (LOCATION); when detected the frequency and location is reported, e.g., FRQ LTG NE, meaning frequent lightning to northeast of station.
(See code details in table below)
RAB07 BEGINNING AND ENDING TIME OF PRECIPITATION AND THUNDERSTORMS w'w'B(hh)mmE(hh)mm; TSB(hh)mmE(hh)mm, where w'w' is the present weather precipitation contraction, B indicates began, E indicates ended; (hh)indicates the hour (reported in UTC) the phenomena began or ended and can be omitted if the hour can be inferred from the report, mm indicates the minutes after the hour the phenomenon began or ended.
VIRGA Augmented to report by human observer; indicates precipitation not reaching the ground is observed.
CIG 013V017 VARIABLE CEILING CIG hnhnhnVhxhxhx;
reported if the ceiling in the body of the report is <3000 feet and variable.
CIG 017 RWY11 CEILING HEIGHT AT SECOND LOCATION CIG hhh[LOC]; Ceiling height reported if secondary ceilometer site ceiling value is different than the ceiling height in the body of the report.
PRESFR PRESSURE RISING OR FALLING RAPIDLY PRESRR or PRESFR; pressure rising or falling rapidly at time of observation.
SLP125 SEA LEVEL PRESSURE SLPppp; sea level pressure reported for ppp in tens, units, and tenths of hPa.
P0003 HOURLY PRECIPITATION AMOUNT Prrrr; in tens, units, tenths and hundredths of an inch since last regular hourly METAR. A trace is reported as P0000.
60009 3- AND 6-HOUR PRECIPITATION AMOUNT 6RRRR; precipitation amount, including water equivalent, to nearest 0.01 inches for past 6 hours reported in 00, 06, 12, and 18 UTC observations and for past 3 hours in 03, 09, 15, and 21 UTC observations. A trace is 60000.
70015 24-HOUR PRECIPITATION AMOUNT 7R24R24R24R24; precipitation amount to nearest 0.01 inches for past 24 hours reported in 12 UTC observation; e.g., 70015 indicates 0.15 inches of precipitation for past 24 hours.
T00640036 HOURLY TEMPERATURE AND DEW POINT TsnTaTaTasnT'aT'aT'a; reported to nearest tenth of oC; sn: 1 if temperature or dew point below 0oC and 0 if temperature/dew point 0oC or higher.
10066 6-HOUR MAXIMUM TEMPERATURE 1snTxTxTx; maximum temperature for past 6 hours reported to nearest tenth of degree Celsius; reported on 00, 06, 12, 18 UTC reports; sn = 1 if temperature below 0oC and 0 if temperature 0oC or higher.
21012 6-HOUR MINIMUM TEMPERATURE 2snTnTnTn; minimum temperature for past 6 hours reported to nearest tenth of degree Celsius; reported on 00, 06, 12, 18 UTC reports; sn = 1 if temperature below 0oC and 0 if temperature 0oC or higher.
400461006 24-HOUR MAXIMUM AND MINIMUM TEMPERATURE 4snTxTxTxsnTnTnTn; maximum temperature for past 6 hours reported to nearest tenth of degree Celsius; reported on midnight local standard time reports; sn = 1 if temperature below 0oC and 0 if temperature 0oC or higher; e.g., 400461006 indicates a 24-hour maximum temperature of 4.6oC and a 24-hour minimum temperature of -0.6oC.
58033 PRESSURE TENDENCY 5appp; the character (a) and amount of change in pressure (ppp) in tenths of hPa for the past 3 hours.
(See code details in table below)
TSNO SENSOR STATUS INDICATORS RVRNO: RVR missing; PWINO: precipitation identifier information not available; PNO: precipitation amount not available; FZRANO: freezing rain information not available; TSNO: thunderstorm information not available (may indicate augmenting weather observer not logged on); VISNO [LOC} visibility at second location not available, e.g. VISNO RWY06; CHINO [LOC}: (cloud-height- indicator) sky condition at secondary location not available, e.g., CHINO RWY06.
$ MAINTENANCE CHECK INDICATOR Maintenance is needed on the system.

Table of Remarks Referring to Type and Frequency of Lightning

Type of Lightning
Type Contraction Definition
Cloud-ground CG Lightning occurring between cloud and ground.
In-cloud IC Lightning which takes place within the cloud.
Cloud-cloud CC Streaks of lightning reaching from one cloud to another.
Cloud-air CA Streaks of lightning which pass from a cloud to the air, but do not strike the ground.
Frequency of Lightning
Frequency Contraction Definition
Occasional OCNL Less than 1 flash per minute.
Frequent FRQ About 1 to 6 flashes per minute.
Continuous CONS More than 6 flashes per minute.

Table of Remarks Referring to Characteristics of Pressure Tendency

Primary
Requirement
Description Code
Figure
Atmospheric
pressure now
higher than 3
hours ago.
Increasing, then decreasing 0
Increasing, then then steady, or increasing then increasing more slowly. 1
Increasing steadily or unsteadily. 2
Decreasing or steady, then increasing; or increasing, then increasing more rapidly. 3
Atmospheric
pressure now
same as 3 hours
ago.
Increasing, then decreasing 0
Steady 4
Decreasing, then increasing. 5
Atmospheric
pressure now
lower than 3
hours ago.
Decreasing, then increasing. 5
Decreasing then steady; or decreasing then decreasing more slowly. 6
Decreasing steadily or unsteadily. 7
Steady or increasing, then decreasing; or decreasing then decreasing moe rapidly. 8


May 2000
UNITED STATES DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration

National Climatic Data Center
NOAA/PA 96052
This document is provided to help users decode airport observations archived at the National Climatic Data Center. Any updates or amendments to the METAR reporting practices can be viewed at the National Weather Service Office of Systems Operations.
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