North Atlantic storm

30°02.3′N 063°54.7′W

Waves left about 19 Sep 22:12Z, ± 7 h

Placed by 2 buoys, whose own placements lie within 15 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