That's reasonable.

I suppose we should be setting ```iScansPositively``` because we're inventing a new ```Nx``` and ```iDirectionIncrementInDegrees```. In fact, it seems very wrong not be be making sure it's explicitly set!

I think we should be basing the lons on ```min(lons)```, not ```lons[0]``` and setting ```iScansPositively``` to 1. I assume it's safe to leave the _'resolution and component flags'_ to the grib api.

Do you agree that's the way to go?

Another good call, @ajdawson.