North Pacific storm

45°40.1′N 155°16.6′E

Waves left about 23 Sep 01:48Z, ± 3 h

Placed by 7 buoys, whose own placements lie within 609 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