North Pacific storm

31°01.0′N 171°47.9′W

Waves left about 17 Sep 14:25Z, ± 3 h

Placed by 3 buoys, whose own placements lie within 390 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