North Pacific storm

37°50.9′N 143°06.2′W

Waves left about 25 Sep 07:00Z, ± 4 h

Placed by 2 buoys, whose own placements lie within 287 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