North Pacific storm

20°15.3′N 158°31.4′W

Waves left about 3 Sep 22:31Z, ± 4 h

Placed by 2 buoys, whose own placements lie within 465 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