North Atlantic storm

42°16.1′N 065°10.7′W

Waves left about 25 Sep 21:24Z, ± 2 h

Placed by 2 buoys, whose own placements lie within 100 km 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