North Atlantic storm

49°36.7′N 015°36.4′W

Waves left about 21 Sep 02:08Z, ± 2 h

Placed by 6 buoys, whose own placements lie within 362 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