North Atlantic storm

40°10.8′N 064°41.0′W

Waves left about 16 Sep 12:49Z, ± 2 h

Placed by 2 buoys, whose own placements lie within 69 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