Copying/plotting GEMAPK grid files from Mercator to Polar stereographic projection

[kwankong]

I am wondering if anyone has had experience copying GEMPAK grid files that are originally in Mercator projection to ones that are in polar stereographic projection. I found that the data that was copied into the polar projection (using GDDIAG) had odd behaviors over the polar regions and especially right around the poles. I suppose the oddities are mathematically related due to the singularity right at the poles. I am attaching a couple of images to illustrate what I am seeing. The red plus signs are grid point locations, and the contours are isobars. Notice that there are no issues around the North Pole with the original dataset in Mercator projection (there is a gap in the isobars right along the Prime Meridian though). However, there are obvious issues with the isobars near the North Pole in the polar stereographic projection (created using GDDIAG).

I appreciate your insights into this issue.