On October 13, 1999, at 1427 hours Hawaiian standard time, a Schweizer SGS-2-33A, N17914, collided with ground obstructions during an off-airport forced landing after encountering an unfavorable wind condition at Waialua, Oahu, Hawaii. The glider, operated under 14 CFR Part 91 as an instructional flight by the Civil Air Patrol, Hawaii Wing, sustained substantial damage. The airline transport pilot was not injured. Visual meteorological conditions existed for the local area flight that had departed from the Dillingham Airfield at 1418. No flight plan was filed. The pilot holds an airline transport pilot certificate for single and multiengine airplanes, and was undergoing instruction to obtain a glider category add-on to his certificate. He was endorsed for solo privileges in gliders. Reported winds, obtained from a remote weather observation facility approximately 15 miles away, were from 060 degrees at 8 knots. The pilot stated that no weather facilities are located at the uncontrolled field, other than windsocks that are located at each end, and at midfield. He stated that the preflight weather briefing forecast was for winds from the northeast consistent with the prevailing northeast trade winds, and runway 8 was in use. The pilot indicated that he also received local weather information from other glider pilots who had been flying prior to his departure. The pilot said that the takeoff was normal, with turbulence experienced at 500 feet above ground level (agl). During the climb he noted that the winds were from the northeast, and were light and variable. He said that at 2,000 feet agl he released the glider from the tow plane and began to lose altitude instead of gaining altitude. He turned to the north, away from a ridge where a strong sink rate had been reported, and proceeded to the practice area. Shortly thereafter, he realized that strong southwesterly winds were creating a strong sink rate condition and he turned toward the airport. When it became apparent that he had insufficient altitude to reach the airport he elected to make an off field landing on a road in an abandoned sugar cane plantation. He believed that the surface winds were still from the northeast and landed on a heading of 080. During the landing rollout the left wing contacted a dirt berm; the glider turned 180 degrees from the initial landing direction and came to rest in a ditch. A Federal Aviation Administration inspector arrived on-scene to inspect the glider an hour later and noted that the winds were from the northwest.