North Pacific storm

48°02.5′N 132°13.9′W

Waves left about 26 Sep 17:17Z, ± 2 h

Placed by 2 buoys, whose own placements lie within 98 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