ATSESS 452 Synoptic Meteorology Friday Lab 08292014 METAR

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 121553 Z 22010 KT 3 SM -RA BR OVC 010 09/08 A 2969 RMK AO 2 RAB 01 E 11 B 45 CIG 007 V 012 SLP 053 P 0000 T 00940078 • 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-CH 12. 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 = 121553 Z • 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 = 21016 G 24 KT 180 V 240 • 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, 180 V 240, indicates a wind shift occurred or it is variable • Calm winds are reported as 00000 KT

Wind Direction/Speed Examples 27005 KT indicates a wind that is blowing from 270 degrees (i. e. from the west) at a speed of 5 knots 16018 G 35 KT indicates a wind that is blowing from 160 degrees (i. e. from the southeast) at a speed of 18 knots with gusts to 35 knots.

Visibility • Example = 1 SM • ‘SM’ is Statute Miles • 10 SM would indicate a visibility of 10 statute miles • 2 1/2 SM would indicate a visibility of 2. 5 statute miles • M at the beginning would mean less than the reported number – M 1/4 SM indicates a visibility of less than 0. 25 statute miles

Runway Visual Range • Example = R 11/P 6000 FT • 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 = SCT 060 • 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 SCT BKN OVC CLR indicates 1/8 to 2/8 sky coverage. indicates 3/8 to 4/8 sky coverage. indicates 5/8 to 7/8 sky coverage. indicates 8/8 sky coverage. indicates clear conditions

Sky Conditions Example SCT 060 indicates 3/8 to 4/8 sky (scattered) coverage by a layer of clouds at 6000 feet above the surface. BKN 039 OVC 100 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/M 01 is temp = 1 C, dew = -1 C

Altimeter Example = A 2990 Always coded with an ‘A’ Given in inches of mercury It is the barometric pressure of the location if it were at sea level • A 2990 = 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 B 13 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 – RAB 07 – 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 (RAB 07 E 24) indicates rain began at 7 after and ended at 24 after the hour

Example Remarks • Sea Level Pressure – SLP 125 – 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 – SLP 125 1012. 5 mb – SLP 955 995. 5 mb

Example Remarks • Hourly Precip Amount – P 0003 – Given in hundredths of an inch. Amount recorded since the last observation – Trace of precip is reported as P 0000 • 6 -Hour Precip – Similarly to hourly, but 60009 • 24 -Hour Precip – Coded with a 7 in front 70009 – Reported at 12 Z, amount recorded in last 24 hours

Example Remarks • Precise Temp/Dewpoint – T 00640036 – 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