El Niño & La Niña — science-based ski prediction for South America's greatest mountains.
The Pacific Ocean is the engine of Andes snow. ONI — the Oceanic Niño Index measured June through August — is our strongest predictor. Unlike Japan, El Niño brings deep snow to the central Andes.
Warm Pacific SSTs push the jet stream south, delivering exceptional moisture to Chile and Argentina. Prime years for Portillo, Valle Nevado, and Las Leñas.
Near-normal conditions. Snowfall variance increases — the South American Mega-Drought index becomes the critical secondary signal during neutral years.
Cool eastern Pacific suppresses atmospheric moisture reaching the Andes. Central Chilean resorts suffer most; Patagonian Catedral remains comparatively stable.
Thirty seasons of data reveal a consistent, actionable link between Pacific Ocean temperatures and Andes snowpack.
Positive correlation — El Niño increases Andean snowfall. Statistically significant at p<0.01 over 30 seasons (1993–2024). Note the sign is opposite to Japan's snowfall relationship.
The model correctly predicts above vs. below-normal snowfall in 77% of seasons — well above the 50% coin-flip baseline. Validated by leave-one-out cross-validation.
Including the South American Mega-Drought binary variable (active 2010–present) raises explained variance to 51.8%. The multi-decadal drought is a structurally separate suppressor.
Selected years illustrating the El Niño signal. Bar length = seasonal snowfall relative to the 30-year mean (257cm).
From the sun-baked central Andes to Patagonian westerlies — ENSO sensitivity varies sharply with latitude and geography.
A transparent, repeatable statistical framework built on 30 years of NOAA climate data and Andes snow records.
We pull the Oceanic Niño Index (ONI) June–August average from NOAA's ERSSTv5 dataset. The JJA window is the strongest Andes predictor, confirmed each November for the season just passed.
Since 2010, the South American Megasequía (mega-drought) has structurally suppressed Andean snowfall. A binary drought variable accounts for this regime shift, lifting model R² from ~0.30 to 0.518.
Ordinary least squares on 1993–2024 data. Portillo seasonal snow depth (cm) is the dependent variable. LOO cross-validation confirms 77% directional accuracy.
Final forecast published each November when NOAA confirms the JJA ONI. Early outlook based on model projections available from September onwards.
Core OLS model for Portillo seasonal snow depth:
The positive ONI coefficient is the defining feature of Andes forecasting — opposite to Japan, where La Niña dominates. The MegaDrought coefficient reflects a structural drying trend that began around 2010.
NOAA CPC — ONI index (1950–present)
Portillo SA — Historical snow depth records
CR2MET — Chile precipitation reanalysis
ENSO Blog — Phase history & classification