North Atlantic storm

37°43.4′N 020°15.7′W

Waves left about 21 Sep 04:12Z, ± 11 h

Placed by 2 buoys, whose own placements lie within 331 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