Corridor Pressure
Elevated
Binding leg: Madeira.
The corridor is only as navigable as its most-pressured link.
Mainstem · Óbidos
Normal
Forecast 61.4th pctile (Normal) · observed 64th
Amazon trunk (Óbidos) — the shared artery both barge legs feed into.
Tapajós · Itaituba
Normal
Forecast 65.8th pctile (Normal) · observed 95th · obs stale
BR-163 → Miritituba/Itaituba → Santarém — the fast-growing Arco Norte leg.
Madeira · Humaitá
Elevated
Forecast 27.9th pctile (Elevated) · observed 17th
Porto Velho → Itacoatiara — Rondônia / west-Mato-Grosso soy & corn.
Alongside ENSO: The Pacific (RONI, FMA predictor -0.45) is not adding compound drought risk this year — the signal is Atlantic-led. On the mainstem and Tapajós, a warm Tropical North Atlantic and El Niño compound — the severe lows need both. The Madeira leg responds to whole-basin Atlantic warmth and is largely ENSO-agnostic.
Red zone (≤10th) = Severe, amber (≤33rd) = Elevated pressure. Forecast is the modelled Sep–Nov low from the spring ocean state; Observed is the most recent river reading. A barge corridor is only as open as its weakest link.
A warm Tropical North Atlantic pulls the Atlantic ITCZ north, starving the Amazon of
wet-season rain and deepening the dry-season river low. Measured in spring, it forecasts
the September–November low months ahead. On the mainstem and Tapajós, El Niño
compounds the Atlantic signal; the Madeira responds to whole-basin Atlantic warmth.
Boreal-spring (Apr–Jun) warmth in this box precedes the Sep–Nov Amazon low by ~3–5 months. The red band (≥ +0.4°C) is the dry-risk regime that drove the 2005, 2010 and record 2023 droughts. Self-computed from NOAA OISST v2.1, 1991–2020 baseline (see fetch_atlantic_index.py).
Óbidos mainstem discharge, leave-one-out (each year predicted from a model fit on all others). Every major drought (2005/2010/2023/2024, red diamonds) was flagged in the driest quartile months ahead. Points near the dotted line = accurate. Out-of-sample skill r ≈ +0.76.