North Pacific storm

47°59.5′N 154°43.0′W

Waves left about 8 Sep 16:19Z, ± 4 h

Placed by 3 buoys, whose own placements lie within 346 km of it

Each buoy places the storm from how its swell's period shortened as it arrived: the longest waves travel fastest. Fronts are drawn at deep-water group speeds along great circles, and stop at land. How it is worked out