North Atlantic storm

42°35.3′N 030°53.8′W

Waves left about 22 Sep 05:35Z, ± 5 h

Placed by 6 buoys, whose own placements lie within 299 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