North Pacific storm

07°47.5′N 139°45.2′W

Waves left about 21 Sep 07:41Z, ± 5 h

Placed by 6 buoys, whose own placements lie within 392 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