North Pacific storm

39°33.8′N 163°48.2′E

Waves left about 16 Sep 23:31Z, ± 5 h

Placed by 3 buoys, whose own placements lie within 498 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