North Atlantic storm

48°41.0′N 010°13.9′W

Waves left about 20 Sep 07:59Z, ± 3 h

Placed by 6 buoys, whose own placements lie within 271 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