Incident Overview
According to the pilot, during the approach to land, thunderstorms were observed in the vicinity of the airport and moisture appeared on the windscreen of the airplane. The pilot elected to continue the approach, subsequently encountering strong turbulence during the base and final legs of the approach.
Turbulence Encounter
While on short final, the airplane was turned 30 degrees to the right of the runway heading, and the nose was forced upward. The pilot regained control and landed firmly on the runway surface. Following touchdown, the airplane departed the left side of the runway, where the left wing "dug" into the grass surface, causing the airplane to cartwheel before coming to rest inverted.
Damage Assessment
The outboard four feet of the left wing and the firewall of the airplane were bent. According to the pilot and a Federal Aviation Administration inspector, there were no mechanical anomalies with the airplane.
Witness Observations
Witnesses observing the flight reported that the wind shifted from a right quartering head wind to a right quartering tail wind and increased in velocity while the airplane was on short final.