North Pacific storm

03°55.8′N 138°40.9′W

Waves left about 21 Sep 00:13Z, ± 6 h

Placed by 5 buoys, whose own placements lie within 173 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