ATS/ESS 452: Synoptic Meteorology

- METAR- The Station Model

What is a METAR?

• Acronym for METeorological Aviation Report• Generated at least once an hour (usually right

prior to the end) or when a significant change in weather occurs

• Composed of two parts: Body and Remarks• Information contained within is added in a

specific order and format

ExampleKHSV 121553Z 22010KT 3SM -RA BR OVC010 09/08 A2969 RMK AO2 RAB01E11B45 CIG 007V012 SLP053 P0000 T00940078

• Information ALWAYS given includes:• Station ID• Date/Time• Wind Speed/Direction• Visibility• Current Observed Weather• Sky conditions• Temperature/Dewpoint• Altimeter Reading (Pressure)

• Any information given after RMK are referred to as remarks, and this information can vary

Web Resources

Station ID Look-up:http://www.nws.noaa.gov/tg/siteloc.shtml

Federal Meteorological Handbook Chapter on METAR:http://www.ofcm.gov/fmh-1/pdf/L-CH12.pdf

Station ID

• Example = KABC• 4 character identifier for reporting stations• The first letter identifies the country. All US

stations begin with ‘K’, Canadian stations begin with ‘C’

• Next 3 characters identify the station.– KJAN is Jackson, MS for example

Date/Time

• Example = 121553Z• Given in Greenwich Mean Time, or Zulu• First two numbers are the day of the month.

Single dates are reported with a 0• Next 4 numbers are the time.

Report Modifier

• Example = AUTO• 3 possibilities: None, AUTO and COR• AUTO means the observation was taken

without human interaction or oversight• COR indicates a correction to a previous report• If nothing, then a human took the observation

Wind Direction and Speed

• Example = 21016G24KT 180V240• First three numbers denote the direction given

in degrees.• The next two numbers are speed in knots• In this example, the G indicates that a gust

occurred.• The second group, 180V240, indicates a wind

shift occurred or it is variable• Calm winds are reported as 00000KT

Wind Direction/Speed Examples

27005KT indicates a wind that is blowing from 270 degrees (i.e. from the west) at a speed of 5 knots

16018G35KT indicates a wind that is blowing from 160 degrees (i.e. from the south-southeast) at a speed of 18 knots with gusts to 35 knots.

Visibility

• Example = 1SM• ‘SM’ is Statute Miles• 10SM would indicate a visibility of 10 statute

miles• 2 1/2SM would indicate a visibility of 2.5

statute miles• M at the beginning would mean less than the

reported number– M1/4SM indicates a visibility of less than 0.25

statute miles

Runway Visual Range

• Example = R11/P6000FT• The first number indicates the runway• Range is given, after the slash, in feet

Present Weather

• Example = -RA BR• The weather occurring at, or in the vicinity of,

the observation point at the time of reporting• There are 5 categories, constructed in

sequences, to consider: Intensity, Descriptor, Precipitation, Obscuration, Other Weather

Present Weather - Intensity

• Example = -RA BR• Intensity: -, +, VC• - = Light (.10”/hour or .01” in 6 minutes)• + = Heavy (.30”/hour or .03” in 6 minutes)• VC = in the vicinity of station• Moderate precip has no symbol

Present Weather - Descriptors

• MI = Shallow• PR = Partial• BC = Patches• DR = Low Drifting• BL = Blowing• TS = Thunderstorm• FZ = Freezing• SH = Shower

Present Weather - Precipitation

• Example = -RA BR• DZ = Drizzle• RA = Rain• SN = Snow• SG = Snow Grains• IC = Ice Crystals• PE = Ice Pellets• GR = Hail• GS = Small Hail/Snow Pellets• UP = Unknown Precip

Present Weather - Obscurations

• Example = -RA BR• BR = Mist• FG = Fog• FU = Smoke• VA = Volcanic Ash• SA = Sand• HZ = Haze• PY = Spray• DU = Widespread Dust

Present Weather - Other

• SQ = Squalls• FC = Funnel Cloud, Tornado or Waterspout• SS = Sandstorm• DS = Duststorm

Present Weather Examples

-TSRA indicates a thunderstorm with light rain.

-RA FG indicates light rain and fog.

Sky Conditions

• Example = SCT060• First three letters represent the amount the

sky is covered• Next three numbers are the height of the

cloud base in hundreds of feet• Up to 3 cloud layers may be reported to a

height of 12,000 feet

Sky Conditions Cont.

FEW indicates 1/8 to 2/8 sky coverage.SCT indicates 3/8 to 4/8 sky coverage.BKN indicates 5/8 to 7/8 sky coverage.OVC indicates 8/8 sky coverage.CLR indicates clear conditions

Sky Conditions Example

SCT060 indicates 3/8 to 4/8 sky (scattered) coverage by a layer of clouds at 6000 feet above the surface.

BKN039 OVC100 indicates 5/8 to 7/8 (broken) sky coverage at 3900 feet and 8/8 (overcast) sky coverage at 10,000 feet.

Temperature/Dewpoint

• Example = 06/04• Temperature is given first, followed by the

dewpoint. Both are rounded to the nearest whole Celsius degree

• Negative readings are coded with a ‘M.’ Example, 01/M01 is temp = 1C, dew = -1C

Altimeter

• Example = A2990• Always coded with an ‘A’• Given in inches of mercury• It is the barometric pressure of the location if

it were at sea level• A2990 = 29.90 inches of mercury

The Remarks Section

• Added only when appropriate• Up to 26 different items can be reported in

this section• ‘RMK’ indicates the beginning of the Remarks

section

Example Remarks

• TORNADO B13 6 NE– Means a tornado began 13 minutes after the hour

and was located 6 miles northeast of the station• PK WND 20032/25– Indicates the strongest (peak) wind since the last

observation– Direction (200), speed of gust (32 knots) and time

of gust (25)

Example Remarks

• Precip Start/Stop Times– RAB07– Coded with type of precip, followed by a B for

began or E for ended– Last numbers indicate minute of the hour the

precip began/end– May be coded together (RAB07E24) indicates

rain began at 7 after and ended at 24 after the hour

Example Remarks

• Sea Level Pressure– SLP125– Given in millibars– SLP stands for sea-level pressure, followed by the last

three digits of the reading– A decimal point is placed between the last two digits– Rule of thumb: If the number is less than 500, place a

10 in front. If more than 500, place a 9 in front– SLP125 1012.5 mb– SLP955 995.5 mb

Example Remarks

• Hourly Precip Amount– P0003– Given in hundredths of an inch. Amount recorded since

the last observation– Trace of precip is reported as P0000

• 6-Hour Precip– Similarly to hourly, but 60009

• 24-Hour Precip– Coded with a 7 in front 70009– Reported at 12Z, amount recorded in last 24 hours

Example Remarks

• Precise Temp/Dewpoint– T00640036– Exact temperature and dewpoint reading to the

tenth of a degree– Begins with a T followed by two 4 digits groups, the

first is temp and the second is dewpoint– The first digit is always the sign; if 0, then the

reading is positive, if 1, then it is negative– In the example, the exact temp = 6.4 degrees C and

dewpoint = 3.6 degrees C