I have added the possibility of NAO() to accept a exp_cor object and then return the NAO forecast in the branch https://earth.bsc.es/gitlab/es/s2dv/-/tree/dev-NAO_fcst?ref_type=heads
If this object is not NULL, the past NAO (using exp or obs depending on the obsproj parameter) is calculated without cross-validation and then projected on the forecast anomalies using .ProjectField function.
Maybe @vtorralba could confirm if she agrees with this procedure.
I think the code already works, and I plan to integrate it into SUNSET to evaluate the results.
Cheers,
Núria