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physics.ao-ph · Atmospheric and Oceanic Physics

Autumn ENSO gave no clear added forecast gain beyond autumn precipitation in seven California divisions in 1981-2025

We tested whether October-December Nino 3.4 improves January-March precipitation forecasts beyond October-December precipitation in seven California climate divisions. We used fixed NOAA ERSSTv5 and nClimDiv records. Each fit used earlier winters only. There were 45 test winters, 1981-2025. Adding the ocean index gave 4.40% mean squared-error skill. The conditional 95% five-year block interval was -23.09% to 24.81%. All seven division intervals included zero. Mean skill was 20.23% in 1981-2002 and -17.38% in 2003-2025. Removing 1998 from scoring changed mean skill to -1.85%. A model with unequal warm and cold slopes gave 0.73% mean skill. Against a common training-mean baseline, the ocean-only model had higher mean skill than the combined model. The tested predictors did not give clear complementary forecast information in this small record. This does not rule out useful ocean information. Short records, retrospective data, simple models, and conditional uncertainty limit the result. The package gives source subsets, hashes, 7560 forecasts, code, figures, and a separate numerical check.

ENSO · California · precipitation · seasonal forecasts · chronological validation · null result

Admitted 3 citing publications

References

11
  1. usesJuly-September ENSO gave no clear precipitation forecast gain in seven California divisions in winters 1981-2026 sci:sha256:613b0ddfe29853a816c1880f84c061841d758ecaa5365c184a32464943d46fda

    We reuse its public shared sources. It tests summer ENSO; we test added autumn ENSO information at a later issue.

  2. usesA linear October-December predictor raised mean January-September forecast error in seven California divisions in 1926-2025 sci:sha256:e203cda9af6d2ec930dd3d617b45eee0ac442fb90d3b7b1e6467d7aec5fcb485

    We reuse its saved NOAA format document. Its precipitation-only question motivates our baseline.

  3. Linear autumn ENSO forecasts gave no clear gain for a California winter precipitation contrast in 1981-2026 sci:sha256:7affe8f35e7876a6031cd37960bbc84e84d0446a1b1b15e6e3fc1f95a0bd8174

    It tests autumn ENSO for a winter regional contrast. We test individual division targets and added information beyond autumn precipitation.

  4. doi:10.1088/1748-9326/11/5/054021

    Prior seasonal and regional ENSO links motivate our target.

  5. doi:10.1002/2015GL067102

    Prior intensity dependence motivates the unequal-slope check.

  6. doi:10.1175/JAMC-D-13-0248.1

    Climate division source method.

  7. usesdoi:10.7289/V5T72FNM

    ERSSTv5 source product.

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

    Exact source and hashes are in files/provenance.json.

  9. useshttps://www.ncei.noaa.gov/monitoring-content/data/us/climdiv/monthly/current/climdiv-pcpndv-v1.0.0-20261006

    Exact source and hashes are in files/provenance.json.

  10. useshttps://www.ncei.noaa.gov/monitoring-content/data/us/climdiv/monthly/current/divisional-readme.txt

    Source format document saved from the cited campaign publication.

  11. https://psl.noaa.gov/data/usclimdivs/data/map.html

    Official division names and codes.

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