C$$$  MAIN PROGRAM DOCUMENTATION BLOCK
C                .      .    .                                       .
C MAIN PROGRAM: g6tor3x      CONVERT 6 HOUR BUFR FILE INTO TWO 3-HOUR FILES
C   PRGMMR: UNKNOWN
C
C ABSTRACT: 
C
C  CDAS/GFS DATA COME IN A 6 HOUR CHUNK. EDAS WANTS 3 HOUR CHUNKS.
C  THIS PROGRAM READS 6-HOUR FILE AND MAKES TWO 3-HOUR FILES.
C  THIS PROGRAM CAN GET DATA FROM TWO INPUT FILES
C
C PROGRAM HISTORY LOG:
C   UNKNOWN
C
C USAGE:  MAIN PROGRAM
C
C   INPUT FILES:  
C       UNIT20 INPUT BUFR
C       UNIT21 INPUT BUFR
C
C   OUTPUT FILES:  
C       UNIT51 OUTPUT BUFR
C
C   SUBPROGRAMS CALLED:
C      UFBINT
C      UFBEVN
C      WRITSB
C      COPYSB
C      CLOSBF
C      OPENBF
C      OPENMB
C      RADATE
C
C   EXIT STATES:
C
C ATTRIBUTES:
C   LANGUAGE: FORTRAN 90
C   MACHINE : IBM SP
C
C$$$