North Pacific storm

12°39.5′N 132°01.7′W

Waves left about 22 Sep 13:43Z, ± 3 h

Placed by 10 buoys, whose own placements lie within 506 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