Great Lakes Wave Explorer

Fresh water, ocean physics, no swell. The Great Lakes build a genuine sea — Superior has produced measured waves over 8 m — but they cannot build a long one. Wave period grows with fetch and duration, and even the longest axis of the largest lake gives a storm only a few hundred kilometres to work with. So the sea here is short and steep: heights that would be unremarkable in the North Atlantic arrive with half the period, which means the waves are far closer together and much harder on a hull. A 3 m 6-second lake sea is a worse ride than a 3 m 12-second ocean swell.

And it arrives fast. The same small fetch that limits the period also means the sea reaches its full height in hours rather than a day, and drops just as quickly. That is why the timeline matters more here than on an ocean basin: a lake forecast is a story about the next twelve hours, not the next six days, and RDWPS runs to +48 accordingly.

Four grids, five lakes. Environment Canada's RDWPS publishes Superior, Huron-Michigan, Erie and Ontario as four separate one-kilometre grids — Huron and Michigan share one because they are hydrologically one lake, joined at the Straits of Mackinac at the same surface level. The picker offers all five as viewports; Michigan and Huron are two views of the same raster.

This is ECCC's model rather than NOAA's GLWU, and the reason is unglamorous: RDWPS publishes each lake on a plain unrotated lat/lon grid, where GLWU is an unstructured triangular mesh that would need its own interpolation pass before it could enter the same pipeline as everything else on this site. Same water, one fewer moving part.

Data © Environment and Climate Change Canada. Forecast Waves is not affiliated with ECCC, and is not a source of marine warnings — see About.