North Pacific storm

51°49.4′N 166°33.1′W

Waves left about 20 Sep 19:40Z, ± 2 h

Placed by 5 buoys, whose own placements lie within 229 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