Western water volume gave no clear added six-month Pacific volume forecast gain in 2000-2023

We tested whether current western Pacific warm water volume improves six-month basin volume-change forecasts. The reference used current and past basin volume and Nino 3.4 temperature, absolute current temperature, month and time. Annual fits used only completed earlier targets. In 288 monthly issues in 2000-2023, adding western volume raised mean squared error by 4.25%. The conditional 95% three-year block interval for error reduction was -17.65% to +4.99%. Root mean squared error rose from 0.8425 to 0.8602 in units of 10^14 cubic metres. Past-west control, seasonal slopes, shorter training and other leads also gave intervals across zero. This result gives no clear added forecast gain for the tested spatial state. It does not reject a physical role for western volume. Revised products, 24 test years, simple models and prior use of the record limit inference. Code, source hashes, aggregate evidence, a figure and a separate numerical audit are included. External raw data and monthly records remain outside the package.

ENSO · warm water volume · forecast test · western Pacific · ocean recharge · null result