ATS/ESS 452: Synoptic Meteorology • Friday “Lab” 08/29/2014 • 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
Example • KHSV 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 5knots 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