An Enter Air Boeing 737-800, registration SP-ESA performing flight E4-503 from Frankfurt/Main (Germany) to Salzburg (Austria), was on approach to Salzburg while a storm system was affecting large parts of Europe, tower reported the surface winds from 270 degrees at 26 knots gusting 46 knots. The aircraft performed a circling approach to Salzburg's runway 33 and was on very short final to runway 33 already in the flare at 10:26L (09:26Z) when a gust caught the aircraft causing the right wing to drop, while the crew counteracted the roll the aircraft touched down hard, the crew initiated a go around and entered the hold at Salzburg VOR. About 5 minutes after the go-around the crew advised they needed to return to Frankfurt, ATC filed a new flight plan. In the meantime two other aircraft went around from very short final (50 feet AGL), one of the crews advised they received a wind shear warning forcing the go-around from about 50 feet AGL. Tower advised the crew of another aircraft "Bei so ca. 50 Fuß über Grund kriegens dann ein paar Watschen" (at about 50 feet AGL you'll receive some clips around the ears), the crew continued the circling approach and subsequently also went around from low height. The Enter Air, after ATC had coordinated the return to Frankfurt, returned to Frankfurt, where the aircraft landed without further incident about 70 minutes after the go around.