The pilot reported that the most recent automated surface observing system (ASOS) weather favored a landing on runway 28, with an 8 knot right quartering headwind and 15 knot gusts. The pilot made a normal approach to runway 28; however, when he reduced engine power and began to flare the airplane ballooned about 8 to 10 ft and he added engine power. During the subsequent touchdown on the main landing gear the wind shifted to a quartering tailwind. The airplane veered to the right and the pilot applied left rudder and brake; however, the airplane ground-looped and exited the runway. The airplane came to rest opposite the landing direction and sustained substantial damage to the fuselage. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. Review of additional ASOS data revealed a 66° difference in the gust wind direction over a 2-minute period around the time of the accident.