Circumstances:
The pilot reported that he had made a normal landing on the grass runway 14. The wind was a light crosswind from the left. During the ground roll the aircraft began to swing to the left. Application of right rudder was not effective, and the aircraft ground looped to the left. During the ground loop the right hand gear leg broke off and the right wing contacted the ground. At the time of the accident there was a thunderstorm developing nearby and strong thermal activity was reported in the circuit area by another pilot. The loss of directional control was probably caused by a sudden wind gust associated with the unstable local conditions.
