The aircraft taxied for runway 27 at Jabiru for a flight to Darwin. There was light rain on the threshold of runway 09 and a wind velocity of approximately 290 degrees at 10 knots with active thunderstorms approaching from the east. After takeoff, the aircraft climbed normally until about 100 feet above ground level, then began to sink. Full power was being indicated on the engine instruments for both engines. However, the pilot noticed that the airspeed was decreasing. He set the best rate of climb speed and selected the landing gear up to reduce drag. The aircraft continued to descend until it struck the runway. It slid along the runway for about 200 metres before stopping. The pilot and passengers vacated the aircraft uninjured. A witness noticed a wind shift as the aircraft commenced its takeoff and it is possible that the aircraft encountered a microburst just after lift off.