North Pacific storm

42°47.5′N 179°19.9′W

Waves left about 4 Sep 22:13Z, ± 2 h

Placed by 6 buoys, whose own placements lie within 598 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