North Atlantic storm

40°19.1′N 056°34.6′W

Waves left about 5 Sep 21:51Z, ± 3 h

Placed by 3 buoys, whose own placements lie within 227 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