I am trying the WC13 4DVAR test case and I am getting this error with my wc13_grd.nc file.
I checked the grd file and the vis_factor variable is not there.   
Any help would be appreciated. 
INITIAL: Configuring and initializing forward nonlinear model ...
 *******
 GET_GRID - unable to find grid variable: visc_factor
            in grid NetCDF file: ../Data/wc13_grd.nc
Elapsed CPU time (seconds):
 Node   #  0 CPU:       0.087
 Total:                 0.610
 Nonlinear model elapsed time profile, Grid: 01
  Allocation and array initialization ..............         0.100  (16.3935 %)
                                              Total:         0.100   16.3935
 Nonlinear model message Passage profile, Grid: 01
  Message Passage: data broadcast ..................         0.420  (68.8524 %)
  Message Passage: data scattering..................         0.014  ( 2.2951 %)
                                              Total:         0.434   71.1475
 All percentages are with respect to total time =            0.610
 ROMS/TOMS - Output NetCDF summary for Grid 01:
 ROMS/TOMS - Input error ............. exit_flag:   2
 ERROR: Abnormal termination: NetCDF INPUT.
 REASON: No error                                                                        
 Node   #  3 CPU:       0.174
 Node   #  1 CPU:       0.175
 Node   #  2 CPU:       0.174