North Pacific storm

21°02.3′N 125°46.6′W

Waves left about 8 Sep 00:07Z, ± 3 h

Placed by 5 buoys, whose own placements lie within 240 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