GfsBcFlather is used to impose "Flather" conditions on the boundaries of a GfsOcean simulation.
The syntax in parameter files is:
GfsBcFlather U [ GfsFunction ] H P [ GfsFunction ]
U is the name of the normal component of the velocity,
H is the name of the depth variable,
P the pressure/elevation variable. The first GfsFunction defines the target normal velocity value and the second GfsFunction the target value of the pressure/elevation.