On September 19, 1994, about 0842 Atlantic standard time, N6844Y, a Piper PA-23-250, registered to the pilot, Mr. Fitzroy Williams, disappeared from radar over the Caribbean Sea, while on a 14 CFR Part 91 personal flight. The weather condition near the accident location are unknown and an IFR flight plan had been filed and activated. The airplane, the pilot and the four passengers have not been found; therefore, the damage is presumed to be destroyed and the injuries are presumed to be fatal. The flight originated from Canefield Airport, Dominica, about 0730 the same day. FAA controllers on duty at San Juan, Puerto Rico, CERAP, stated that the pilot had reported over ILURI intersection on Amber 555 airway at 8,000 feet. Shortly thereafter about 0842, the controller lost radar and radio contact with the airplane. The last recorded radar contact with the airplane was at 7,800 feet about 16 miles northwest of ILURI intersection. The U.S. Coast Guard conducted air and sea searches with negative results. A review of available weather satellite data revealed that an area of intense and building showers and thunderstorms along the Amber 555 airway, in the vicinity of where radar contact with the flight was lost.