Tomamu JP
The short answer: PassCast projects a median of 155" at Tomamu for 2026-27 — 89% of a typical season — with a skiability rating of 41/100, ~4 powder days, and Dec–Jan as the prime window. Updated daily from 10,000 simulations.
80% of simulated seasons land between 111" and 201". Reseeded daily as ENSO observations, CPC outlooks, and SEAS5 runs update.
10,000 simulated 2026-27 seasonsENSO-weighted resampling of 36 real seasons (1990–2026) at Tomamu, tilted by the live seasonal outlook
Highlighted bars span the middle half of outcomes (P25–P75). The yellow dashed line is a typical season — the median of the last 36 at this mountain.
What's driving this forecast
The 2026-27 season is simulated by resampling Tomamu's historical seasons weighted toward El Niño analog years. NOAA CPC El Niño Advisory (June 11, 2026): El Niño conditions are present and expected to strengthen into winter 2026-27, with a 63% chance of a very strong event (Niño3.4 ≥ +2.0°C) during Nov-Jan. CPC DJF strength odds: very strong 46%, strong 33%, moderate 16%. IRI (June 22) concurs at 98% El Niño for DJF. Latest observed ONI (AMJ 2026): +1.0.
El Niño weakens the East Asian Winter Monsoon — fewer Siberian cold surges across the warm Sea of Japan means fewer sea-effect powder days (Ueda et al. 2015). El Niño seasons average ~6% less snowfall nationally, but 1997-98 and 2015-16 cut low-elevation Honshu to near half of normal; Hokkaido and high terrain are most resilient. Applied as a -4% tilt at partial weight.
The 51-member SEAS5 seasonal forecast puts Nov–Jan snowfall at this grid point at 90% of its ERA5 normal (ensemble mean 81", spread 60–105"). Applied as a -3% tilt — experimental, heavily shrunk and clamped because seasonal models and reanalysis have different biases.
Day-to-day weather models have no skill this far out, so the near-term forecast contributes 0% weight today. The simulation leans entirely on ENSO-conditioned climatology — exactly what an honest seasonal outlook should do in summer. Weighting shifts toward live forecasts as opening day approaches.
The regional readJapan · from the 2026-27 outlook
A strong El Niño weakens the East Asian Winter Monsoon, and fewer Siberian cold surges across the Sea of Japan means fewer of the sea-effect powder days that make Japanuary. The strong-event analogs matter: 1997-98 and 2015-16 were two of Japan's leanest, latest-starting winters, with some low Honshu resorts near half of normal; 2023-24 began painfully late before February rescued Hokkaido. Expect a delayed start, rain events at low-elevation Honshu areas, and the best resilience in Hokkaido (Niseko, Rusutsu) and high-altitude Honshu. Aim for mid-January to mid-February — unless the Arctic Oscillation goes strongly negative, the one wildcard that can override El Niño entirely.
Month by monthENSO-conditioned analog medians vs a typical month — when this season should deliver
Prime window: Dec–Jan — the deepest contiguous stretch of the conditioned season. Aim the trip there.
The analog poolEvery season since 1990 at Tomamu (ERA5, calibrated to the resort's reported average), colored by ENSO phase
Pass math for Tomamu
Tomamu isn't on a multi-resort pass — but you can still see what a season here is worth.
No multi-resort pass covers these mountains — window tickets are the play.
Tomamu 2026-27: straight answers
- How much snow will Tomamu get in the 2026-27 season?
- PassCast's latest 10,000-run simulation (reseeded 2026-07-10) puts the median at 155 inches — 89% of a typical season at Tomamu — with 80% of outcomes between 111 and 201 inches. The forecast blends Tomamu's own 36-season ENSO analog record with NOAA's seasonal outlook and the ECMWF SEAS5 ensemble.
- Is a season pass worth it for Tomamu in 2026-27?
- Tomamu is not on Epic, Ikon, or Mountain Collective for 2026-27 — budget about $51 per peak-window day ticket, or check the resort's own multi-day products.
- When is the best time to ski Tomamu in 2026-27?
- Dec–Jan is the prime window — the deepest contiguous stretch of the ENSO-conditioned season at Tomamu. Month-by-month medians are charted on this page.
- How reliable will the snow be at Tomamu this season?
- The simulation gives Tomamu a 29% chance of beating its typical season and a median of about 4 six-inch-plus powder days. Its skiability rating is 41/100 (“Selective — time it well”), updated daily.
Sources: ERA5 reanalysis & multi-model forecasts via Open-Meteo · NOAA CPC ONI, ENSO advisory & seasonal outlook · ECMWF SEAS5 · pass prices verified July 2026. See methodology for the honest fine print.