North Pacific storm

45°50.5′N 140°08.3′W

Waves left about 19 Sep 01:58Z, ± 3 h

Placed by 3 buoys, whose own placements lie within 143 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