North Pacific storm

15°39.0′N 145°38.0′W

Waves left about 4 Sep 01:28Z, ± 5 h

Placed by 2 buoys, whose own placements lie within 535 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