North Pacific storm

17°44.2′N 165°19.3′W

Waves left about 7 Sep 12:11Z, ± 2 h

Placed by 2 buoys, whose own placements lie within 216 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