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physics.ao-ph · Atmospheric and Oceanic Physics

A spring Pacific temperature contrast gave no clear added winter forecast gain in a linear test for 1981-2024

We tested whether the March-May Nino 1+2 minus Nino 4 temperature anomaly adds skill for the following December-February Nino 3.4 anomaly. The baseline used spring strength, its change from winter, and an absolute centered-strength term. We used a fixed NOAA CPC ERSSTv5 table, 30 initial training years and 44 forecasts from 1981 to 2024. Each fit used earlier origin years only. The contrast reduced mean squared error by 0.0101 C squared, or 1.31%. The conditional 95% five-year block interval was -0.0804 to 0.1015 C squared. Root mean squared error changed from 0.8774 to 0.8716 C. The gain was positive in the first half and negative in the second half. All planned model checks had intervals that included zero. Thus, this test gives no clear added forecast gain. It does not show equal skill or identify a physical cause. One revised SST product, few independent events, model form and conditional uncertainty limit the result. The package includes the source snapshot, each forecast, code, uncertainty draws and an independent numerical audit.

ENSO · spring · forecast validation · Pacific temperature contrast · null result · block bootstrap

Admitted 1 citing publication

References

9
  1. usesA winter Pacific temperature contrast gave no clear next-winter prediction gain with an asymmetric strength baseline in 1981-2025 sci:sha256:052912e523273b0db9cc3a13e6f7f1ccfb2c72565d6e9b88a4e004b308ed207a

    Published prior evidence sets the question and benchmark scope. The records overlap; this is not independent data confirmation.

  2. usesWarm and cold slopes gave no clear six-month ONI forecast gain in two NOAA records for 1981-2024 sci:sha256:c447fb2c559287cf4b4d6677e63b3c44aecc4e1405d2bb93f935a1fa8e0af5e2

    Published prior evidence sets the question and benchmark scope. The records overlap; this is not independent data confirmation.

  3. usesThree-month Nino 3.4 forecasts had lower May skill but no clear May error increase over November in 1981-2025 sci:sha256:ca30a058ef538c74350e2f2c5b11ecd2ba9218b7838aeee4a2821b453bc09445

    Published prior evidence sets the question and benchmark scope. The records overlap; this is not independent data confirmation.

  4. doi:10.1175/JCLI-D-17-0180.1

    Prior study of forecasts near the spring barrier and use of other ocean and atmosphere predictors. We do not repeat its model.

  5. doi:10.1175/JCLI-D-22-0013.1

    Prior distinction between persistence and prediction barriers. This study tests an added predictor after spring, not the barrier itself.

  6. doi:10.1175/1520-0442(2001)014%3C1697:LIOENO%3E2.0.CO;2

    Prior normalized east-west Nino contrast. Our main contrast is raw and not the filtered Trans-Nino Index.

  7. doi:10.7289/V5T72FNM

    NOAA ERSSTv5 source product.

  8. https://www.cpc.ncep.noaa.gov/data/indices/ersst5.nino.mth.91-20.ascii

    Exact public source URL for the saved raw table.

  9. https://psl.noaa.gov/data/climateindices/list/

    Regional bounds and identification of the CPC ERSSTv5 table.

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