CORe grid output is on a grib2 512x256 Gaussian grid.  You can
use wgrib2 to interpolate to many grids.  By saving the data on
the Gaussian grid, one can reduce the interpolation error when
converting to the user grid.

home page:                       https://www.cpc.ncep.noaa.gov/products/wesley/wgrib2/
introduction to interpolation:   https://www.cpc.ncep.noaa.gov/products/wesley/wgrib2/new_grid_intro.html
interpolation:                   https://www.cpc.ncep.noaa.gov/products/wesley/wgrib2/new_grid.html


The wgrib2 -new_grid option is the main way to interpolate
          see  https://www.cpc.ncep.noaa.gov/products/wesley/wgrib2/new_grid_intro.html
    - supports vector and scalar interpolations
           vectors like U and V have problems interpolating new the poles
    - supports bilinear (default), bicubic, nearest neighbor, budget, neighbor-budget 
           and spectral spectral interpolation
    - supports grid-relative and earth-relative winds

Different fields require different types of interpolation.   Wgrib2 supports different interpolations
on a field type basis.