DESIRE 

     DESIRE is the value of the output vertical coordinate variable
     to which the input variables should be interpolated.  For example,
     to interpolate the input variables to the PV surface PV = 1.5 PVU,
     DESIRE should be set equal to 0.0000015.  

     DESIRE and GDOUTL are specified separately because GEMPAK requires
     vertical levels in grid files to be integers.  For example, by
     convention, for the PV surface PV = 1.5 PVU, an output grid level
     of 0.0000015 is not allowed.  By convention, one could specify
     this level as GDOUTL = 15.