North Pacific storm

48°54.7′N 138°27.4′W

Waves left about 27 Sep 09:57Z, ± 3 h

Placed by 2 buoys, whose own placements lie within 138 mi 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