Spring water volume gave no clear added winter ENSO forecast gain after surface history in 2001-2024

We tested whether March-May equatorial Pacific warm water volume adds next-winter forecast value after spring surface temperature, its recent change, and an older winter are known. We used fixed NOAA GODAS and CPC ERSSTv5 RONI and ONI snapshots. Each linear fit used earlier years only. There were 24 target winters in 2001-2024. Adding volume raised RONI mean squared error by 4.44%. The conditional 95% three-year block interval for error reduction was -57.70% to 30.59%. ONI error fell by 1.89%, with limits of -61.32% to 34.02%. All planned primary-comparison checks had intervals that include zero. Thus this test does not establish added skill from volume after surface history. It also cannot distinguish a useful effect from a harmful one. The short record, revised data, linear models and conditional intervals limit inference. The result does not reject ocean recharge or measure operational forecast skill. The package includes public domain annual inputs, exact source hashes, code, all predictions, scores, numerical checks and a figure.

ENSO · ocean memory · warm water volume · RONI · ONI · forecast validation · null result