WRF

On 17 May 2007 a bug was reported. It had been assumed that the data were of the "native grid" type. This assumption was not correct. There is an easy work around. Change

     res@tfDoNDCOverlay = True        
     to 
     res@tfDoNDCOverlay = False

and add

     x@lat2d  = lat2d
     x@lon2d  = lon2d

This forces NCL to compute the appropriate coordinate transformations.