North Atlantic storm

39°42.8′N 013°55.6′W

Waves left about 20 Sep 04:47Z, ± 5 h

Placed by 3 buoys, whose own placements lie within 365 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