NMC ON124 describes in detail the format for the surface reports.
There are no longer any separate header records in these data files.
The first 10 characters of each record contain the year, month, day, and
hour (2x,4i2) of each observation and the original NMC record begins in the
11th character of the record.


Descriptions of the variables contained in the tables of the format
description is needed to interpret the values returned by the read
program.

EXAMPLE

Call to cat52 unpack

C
C READ CATEGORY 52 DATA
      CALL SADP52(MCNT,XPC6,XSNO,XPC24,IPCT,IPRW,IZW,IDDW,IPRS,
     2 IZS,SST,ISPH,ISPHD,ISDD,ISFF,XWEQ)

Excerpt from format.on124 describing catagory 52 data with fortran
variable names added. Note variables in call are in the same order
as they appear in the table.

     Category 52 - Surface Data (40 characters each)

     No. of Characters                 Parameter                           Unit

XPC6         4           Amount of precipitation past 6 hours*   Hundredth of an inch
XSNO         3           Total depth of snow on ground**         Inch
XPC24        4           Total precipitation past 24 hours*      Hundredth of an inch
IPCT         1           Duration of precipitation observation   Number of 6-hour periods
IPRW         2           Period of waves***                      Second
IZW          2           Height of waves                         Half meter
IDDW         2           Direction from which swell waves        WMO code table 0877
                           are moving
IPRS         2           Period of swell waves                   Second
IZS          2           Height of swell waves                   Half meter
SST          4           Sea surface temperature                 Tenth of degree C
ISPH         2           Special phenomena, general              ****
ISPHD        2           Special phenomena, detailed             ****
ISDD         1           Ship's course                           WMO code table 0700
ISFF         2           Ship's average speed                    WMO code table 4451
XWEQ         7           Water equivalent of snow and/or ice     Hundredth of an inch



     *      Trace is output as 9998.

     **     Trace is output as 998.

     ***    No estimate due to confused sea--output as 98.

     ****   Special phenomena, general, is missing (99) only if special
            phenomena, detailed, is missing (99).