North Pacific storm

10°31.2′N 144°19.3′W

Waves left about 2 Sep 11:42Z, ± 4 h

Placed by 4 buoys, whose own placements lie within 563 km 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