North Atlantic storm

43°48.1′N 023°50.3′W

Waves left about 21 Sep 05:28Z, ± 3 h

Placed by 4 buoys, whose own placements lie within 412 nmi 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