North Pacific storm

40°37.9′N 156°03.2′E

Waves left about 22 Sep 13:09Z, ± 3 h

Placed by 7 buoys, whose own placements lie within 525 nmi 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