North Pacific storm

48°38.2′N 171°54.6′E

Waves left about 24 Sep 07:16Z, ± 3 h

Placed by 7 buoys, whose own placements lie within 431 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