North Atlantic storm

41°57.8′N 063°50.1′W

Waves left about 24 Sep 10:46Z, ± 2 h

Placed by 4 buoys, whose own placements lie within 140 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