HISTGRD toggles the writing of the graph-to-grid history grid to
the GEMPAK grid file. The history grid contains integral values
which indicate which method was used to assign the data grid value.
The grid is primarily a diagnostic tool and is usually not saved.
yes - save history grid
anything else - do not save history grid
The name of the history grid will be the name of the data grid
concatenated with "HIST", e.g., data P06I will be P06IHIST.
The vertical coordinate and level will be the same as the data grid.