North Pacific storm

36°09.2′N 146°41.2′W

Waves left about 20 Sep 15:52Z, ± 3 h

Placed by 3 buoys, whose own placements lie within 191 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