ASCII Surface Data File

This type of file is generated by the surface METAR/SAO decoder (sfcdec) and the synoptic decoder (syndec) 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: 21Z 1 MAY 20

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:

KEWB 011153Z 18014G19KT 1 3/4SM RA BR OVC006 12/12 A2980 RMK AO2
     SLP089 P0013 60059 70059 T01220122 10122 20117 55009=

The above line would be decoded into the following format:

KEWB 540 540 1814 980  89 1.75 6O !RA_BR @1153 P5 -9 r59 R59 x54.0 n53.1 G 19 #AO2 P0013  $

A sample surface converted file would look like:

WXPSFC
12Z  1 MAY 20
LMML 734 536 2916   7 -99 -99 -99M !CAVOK @1145 #NOSIG  $
K79S 464 428 1909   0 -99 10.0 -99M - @1145 G 14 $
KS71 464 464 3110 991 -99 10.0 -99M - @1145 $
ENBR 482 374 1005 947 -99 -99 30F,45B - @1150 #NOSIG RMK WIND 1200FT 12010KT  $
ENBO 464 230 1014 974 -99 10.0 -99C - @1150 #NOSIG  $
ENDU 374 284 1906 977 -99 -99 35F,45B - @1150 #NOSIG RMK WIND 1100FT 20010KT WIND 2200FT 20011KT  $
ENGM 428 410 0002 950 -99 -99 2F,4S,20B !-RA @1150 #NOSIG  $
ENOL 518 338 1316 950 -99 -99 30F - @1150 #NOSIG  $
ENVA 500 302 1412 953 -99 -99 45S - @1150 #NOSIG RMK WIND 670FT 14019KT  $
...

FILES

• sao.cty -- METAR station location database.
• syn.cty -- used as cross reference between WMO number and ICAO ID.

SEE ALSO

• sfcdec
• syndec
• sfcplot
• sfctext
• meteoplot

Last updated May 1, 2020