North Pacific storm

50°53.8′N 178°46.9′W

Waves left about 19 Sep 10:53Z, ± 2 h

Placed by 11 buoys, whose own placements lie within 443 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