GUESFUN

     GUESFUN specifies one or more grid diagnostic functions that compute
     the first guess grid for a Barnes objective analysis.  If more than
     one functions are specified, they must be separated by semicolons.
     For more information, see the GPARM documentation.

     GUESFUN may contain in-line values for the times, levels and vertical
     coordinate. These values are used to override the analysis time, level
     and vertical coordinate for the guess grid. However, the time has a 
     special feature. In order to proceed, the application must be able to 
     set a default time for the guess grid. This is done by using the 
     analysis time and the grid file cycle time to find the matching
     analysis or forecast time from the grids. The feedback from the
     application will show the default time even if the user has set an
     in-line value for the guess grid time. However, the in-line value will
     override the analysis time when the grid is computed. If a default
     time cannot be created, even if the in-line value is valid, the
     application will stop processing.