North Atlantic storm

44°29.4′N 039°57.3′W

Waves left about 23 Sep 13:00Z, ± 5 h

Placed by 4 buoys, whose own placements lie within 252 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