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ASCII Surface Data File

This type of file is generated by the surface METAR/SAO decoder (sacvt) and the synoptic decoder (smcvt) programs for use with other WXP surface display programs.

FORMAT

This is an ASCII format which makes the files editable by programs such as "vi" and "emacs".  The format of the file is as follows:

WXPSFC
hhZ dd mmm yy
iii TTT ddd wwww aaa ppp vvv hhhC[,hhhC...] WWW [@tttt] [LAAAA,OOOOO] [PTttt][QRRR] [rrrr][qrrr] [RRRR] [Xxxx] [Nnnn] [Tee] [SSS] [Cccc] [Ggg] [ssss] [#cccccc...] $
iii TTT ddd wwww aaa ppp vvv hhhC[,hhhC...] ... $
...

Header Format

The first line of the file is the string:

WXPSFC

which is used to determine file type. The second line of the data file contains the date and time in the following format:

hhnnZ dd mmm yy

Where:

  • hh -- Hour of the observation in GMT.
  • nn -- Minute of the observation (optional).
  • dd -- Day of the observation.
  • mmm -- A three letter abbreviation for the month.
  • yy -- The last two digits of the year.

Example: 12Z 24 JUN 98

Data Line Format

The data are entered on the following lines, one station per line. Each particular piece of information is separated by a space and the line is terminated with a space and a "$". The format for each station is listed below:

iii TTT ddd wwww aaa ppp vvv hhhC[,hhhC...] WWW [@tttt] [LAAAA,OOOOO] [PTttt][QRRR] [rrrr][qrrr] [RRRR] [Xxxx] [Nnnn] [Tee] [SSS] [Cccc] [Ggg] [ssss] [#cccccc...] $

Where:

  • iii -- Station identifier. If the station does not have an ICAO ID and the id_enc option is specified, an ID will be derived from the WMO number using the 2 letter country prefix and the last 3 numbers of the WMO number.  Country prefixes are listed in the Global Station Information Appendix.
  • TTT -- Temperature in .1_F. Missing data is -99.
  • ddd -- Dewpoint in .1_F. Missing data is -99.
  • wwww -- Wind data. If wwww is 4 digits, the first two digits are the direction in 10's of degrees and the last two digits are the wind speed in knots. If wwwwww > 5000, the first 3 digits are the wind direction in degrees and the last 3 digits are the wind speed. Missing winds are encoded -999.
  • aaa -- Altimeter setting in .01 inches of Mercury. Only 3 digits are displayed. To convert to real altimeter setting: 30+aaa/100 if aaa is less than 500, otherwise, 20+aaa/100. If aaaa is a four digit number, the altimeter setting is aaaa/100. Missing data is -99.
  • ppp -- Sea level pressure in .1 millibars. Only 3 digits are displayed. To convert to real altimeter setting: 1000+ppp/10 if ppp is less than 500, otherwise, 900+ppp/10. This can be modified by checking altimeter setting, if altimeter setting > 30.8" or temperature < -40_F, 1000 is added. If altimeter setting < 28.3, 900 is added. If pppp is a four or five digit number, the pressure is pppp/10. Missing data is -99.
  • vvv -- Visibility in miles. Missing data is -99.
  • hhhC -- Cloud base hhh in 100's of feet and cloud cover C. Multiple levels can be specified separated by commas.(-99 for missing) Cloud cover can be:
    C-clear, F - few, S-scattered, B-broken, O-overcast, X-obscured, M - missing, s, b, o, x-thin layers, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9-Eighths of sky coverage with 9 being obscure.
  • W -- Present weather. This is the standard SAO weather string (i.e. RW-F).
    If weather has a leading !, this is the METAR string (i.e. -RA).
    If the weather is a number, it refers to the 2 digit international coding table.
    Missing data is '-';
  • @tttt -- Observation time (HHMM). (OPTIONAL)
  • LAAAA,OOOOO -- The latitude and longitude of the station in .1 degrees. (OPTIONAL)
  • PTttt -- Pressure tendency in .1 millibars/three hours. The first digit "T" represents the type of fall or rise. (0-3:rise, 5-8:fall). The remaining three digits represent the tendency. (OPTIONAL)
  • QQQQ -- 3 hours precipitation in .01 inches. (OPTIONAL)
  • rrrr -- 6 hour precipitation in .01 inches. (OPTIONAL)
  • qqqq -- 12 hour precipitation in .01 inches. (OPTIONAL)
  • RRRR -- 24 hour precipitation in .01 inches. (OPTIONAL)
  • Xxxx -- Maximum temperature in F. (OPTIONAL)
  • xxxx -- 6 hour maximum temperature in F. (OPTIONAL)
  • Nnnn -- Minimum temperature in F. (OPTIONAL)
  • nnnn -- 6 hour minimum temperature in F. (OPTIONAL)
  • Tee -- Extreme temperature in F. (OBSOLETE - OPTIONAL)
  • Sss -- Snow cover in inches. (OPTIONAL)
  • Cccc -- Cloud types for low, medium and high clouds. (OPTIONAL)
  • Ggg -- Wind gusts in knots. (OPTIONAL)
  • ssss -- Solar radiation in minutes. (OPTIONAL)
  • tttt -- Sea Surface temperature in _C. (OPTIONAL)
  • pppp -- Sea wave period in seconds. (OPTIONAL)
  • hhhh -- Sea wave height in meters. (OPTIONAL)
  • cccc... -- Comments (up to 34 characters).(OPTIONAL)

EXAMPLES

Example of raw surface data:

KIND 091756Z 16012KT 2 1/2SM RA BR SCT040 OVC046 07/06 A3002 RMK
     AO2 PRESFR SLP170 P0012 60017 T00670061 10072 20033 58036
     $=

The above line would be decoded into the following format:

KIND 441 430 1612   2 170 2.5 40S,46O !RA_BR @1756 P8-36 r17 x45.0 n37.9 #AO2 PRESFR P0012  $

A sample surface converted file would look like:

WXPSFC
1800Z  9 MAR 97
WRN 122  -4 3223 -99 263 9.0 -99M M @1745 G 29 #M/ 7007  $
WZN -99 -99 3515 -99 -99 -99 -99M M @1747 G 20 #M/M 7018  $
WBK 104 -22 3215 -99 299 9.0 -99M M @1746 #7009  $
KHKY 608 374 0908  43 -99  15 50S,90O - @1752 P7-19 x61.5 n37.0 #SLPNO  $
KMWC -99 -99 1907 988 -99 1.0 6O !-RA_BR @1745 $
KTRK 340 261 0000  42 -99  30 180S - @1745 n18.0 #NOSPECI  $
KART 284  32 3105  51 340  15 -99C - @1748 P7-20 x29.5 n-4.7 $
...

FILES

  • syn.cty -- used as cross reference between WMO number and ICAO ID.

SEE ALSO


For further information about WXP, email technical-support@weather.unisys.com
Last updated by Dan Vietor on August 3, 1998