On November 11, 1999, at 1247 hours Pacific standard time, a Diamond Aircraft Industries (Katana) DA 20-A1, N183DA, veered off runway 01R and struck a windsock pole between the runway and taxiway at Buchanan Field, Concord, California. The airplane, owned and operated by Concord Flight International under 14 CFR Part 91 as an instructional flight, sustained substantial damage. The student pilot, the sole occupant, was not injured. Visual meteorological conditions existed for the local area instructional flight and no flight plan was filed. The student pilot stated that he had gone up to practice touch-and-go takeoffs and landings. On the first touch-and-go landing he noted that he was too high and initiated a go-around. The next two touch-and-go takeoffs and landings were executed with no discrepancies. He stated that on short final for the third one, the airplane was blown slightly off centerline. He returned the airplane to centerline and stated that there were no further discrepancies with the approach. The airplane landed on centerline just past the runway numbers, and he "got rid of a notch of flaps, and pushed the carburetor heat in." The pilot stated that he advanced the throttle and the airplane "snapped" to the left. He applied right rudder, which stopped the turn to the left, but did not return the airplane to the runway. The airplane continued off of the runway before he reduced the throttle. The pilot stated that he did not apply brakes at any time and that there were no perceived anomalies with the flight control system. The left wing of the airplane struck the windsock pole and the airplane came to rest on a westerly heading from the direction of travel. The right main landing gear was ripped off and the engine was still running. The pilot shut the airplane down and notified the tower that he was all right via a handheld radio. According to a Federal Aviation Administration inspector, there were no signs of a skid mark present on the runway, grass, gravel, asphalt, or dirt areas where the accident occurred. He conducted an inspection of the airplane's rudder, braking system and wheels and observed no abnormalities. The aviation surface weather report for the airport was reporting winds from 360 degrees at 8 knots.