OVERWR

     OVERWR allows the user to specify whether existing GEMPAK grids in a 
     file should be overwritten or left unchanged.
     The valid choices for the flags are "YES", or "NO".

     If OVERWR is set to "YES", and the program tries to write out a grid 
     that already exists in the output GEMPAK file, the grid will be replaced 
     with the new one.  Otherwise, the original grid remains the same and 
     the new grid is not written out to the file.

     Note that the "YES" option does not overwrite the grid navigation in 
     the header of the output GEMPAK file nullifying all the existing grids.  
     Only grids with the same navigation that is specified in the output file 
     header can be written.

     Examples:

	OVERWR =	yes		--	existing grid is overwritten.

	OVERWR =			--	existing grid is NOT
						overwritten.

	OVERWR =	no		--	existing grid is NOT
						overwritten.