North Atlantic storm

47°06.3′N 045°15.5′W

Waves left about 23 Sep 04:17Z, ± 5 h

Placed by 5 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