Every atmospheric river to reach the West Coast
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Rivers by water year
Landfalling atmospheric rivers in each water year (October to September), by the highest AR scale rank reached anywhere on the coast. Choose a stretch of coast to count only the rivers that peaked there.
Table of this chart
Where and when they land
Left: how much of each month the coast spends in AR conditions (vapor transport of 250 kg m⁻¹ s⁻¹ or more), from San Diego at the bottom to Cape Flattery at the top. Right: ranked rivers a year at each latitude.
The archive
The strongest events can be replayed on the globe from ERA5, six hours at a time. Pick one from the table.
| AR scale | Dates (UTC) | Peak IVT | Strongest near | Duration | Coast reached | Water year | Replay |
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How this was built
Vapor transport comes from ERA5, the ECMWF reanalysis: the vertically integrated water vapour flux every six hours on a 0.25° grid, read from the public ARCO ERA5 store. The coast is sampled every half degree of latitude from 32.5°N to 49°N, one degree offshore. A landfalling event starts when the first of those points reaches 250 kg m⁻¹ s⁻¹ and ends when the last one drops below it; neighbouring latitudes that are in AR conditions at the same time belong to the same event. Its rank is the highest AR scale rank (Ralph and others, 2019) that any one point reaches, from that point's own peak and duration. With six-hourly data, durations come in steps of six hours, and back-to-back storms that never let the coast drop below 250 count as one long event. Spells too weak and short to rank are kept in the archive as unranked.