Does ENSO information improve subnational forecasts of acute food insecurity across Africa's East–Southern dipole? A preregistered Bayesian study with a prospective test on the 2026–27 El Niño (Protocol v1)

Preregistered protocol, frozen analysis data and processing code for an area-level Bayesian study of whether El Niño–Southern Oscillation (ENSO) information improves probabilistic forecasts of FEWS NET acute food-insecurity phases in 2,978 subnational areas of eight countries (Ethiopia, Kenya, Somalia, Uganda; Malawi, Mozambique, Zimbabwe, Madagascar). The model is a cumulative-logit ordinal model with a measurement layer for classification noise, BYM2 spatial and RW1 temporal effects. Confirmatory hypotheses: H1, ENSO/IOD information improves out-of-sample ranked probability skill over a history-only baseline; H2, ENSO effects follow the local rainfall teleconnection; H3, prospective projections for the Feb 2027 (both regions) and Jun 2027 (Southern Africa) assessments, issued from information available on 18 and 28 Aug 2026, are at least as skilful as FEWS NET's own projections. The package holds the protocol (PDF), a SHA-256 manifest, 16 frozen data files, the Python scripts that rebuild them from the raw downloads, and the Earth Engine and Copernicus download notebooks. No relationship between ENSO and any food-security outcome was estimated before this deposit. The projections will be committed by hash in version 2 before the October 2026 FEWS NET release.