North Atlantic storm

40°16.2′N 041°32.2′W

Waves left about 3 Sep 14:41Z, ± 9 h

Placed by 2 buoys, whose own placements lie within 652 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