Perhaps an attempt should be made to let a new model learn how to forecast on it's own. The chess super computer Alpha Zero learned to play extremely high level chess by playing thousands upon thousands of games of chess against itself. The computer has never "seen" a game played by humans or other computers. The computer"learned" by trial and error. I am far from a computer expert although I did stay at a Holiday Day Inn Express last night but I wonder if a similar development can be taken to develop a new and much better weather model.
From the Wiki article
AlphaZero was trained solely via "self-play" using 5,000 first-generation TPUs to generate the games and 64 second-generation TPUs to train the neural networks, all in parallel, with no access to opening books or endgame tables. After four hours of training, DeepMind estimated AlphaZero was playing chess at a higher Elo rating than Stockfish 8; after nine hours of training, the algorithm defeated Stockfish 8 in a time-controlled 100-game tournament (28 wins, 0 losses, and 72 draws).[1][2][3] The trained algorithm played on a single machine with four TPUs.