New blog post here:
https://geoenergymath.com/2019/05/02/implicit-interpolating-cross-validation-of-enso/

What's unnerving about the model is that although the results are excellent, there may be a few minor factors that are missing. I kind of miss having an automated symbolic reasoning tool like Eureqa available. It would definitely help to find any second-order modifications.

(from what I can tell, Eureqa went from being a proprietary but free tool, to being a paid subscription-only service, and then sold off to an AI business forecasting company. The author of the software probably made a mint)