DURING THE PRE-FLT WX BRIEFING, THE NON-INSTRUMENT RATED PLT WAS ADVISED OF NUMEROUS THUNDERSTORMS ALONG HIS PROPOSED ROUTE OF FLT & THAT VFR FLT WAS NOT RECOMMENDED. WHILE EN ROUTE, HE CONTACTED MIAMI CENTER, REQUESTED FLT FOLLOWING & WAS INSTRUCTED TO MAINTAIN VFR. IN THE VICINITY OF NUMEROUS LVL 3 & 4 PRECIPITATION AREAS, THE PLT INQUIRED ABOUT THE WXAHEAD & WAS PROVIDED VECTORS TO THE CLEAREST AREA. HOWEVER, RADIO & RADAR CONTACT WERE LOST & THE ACFT CRASHED. A WITNESS NEAR THE CRASH SITE SAW THE ACFT FALLING WITHOUT WINGS JUST PRIOR TO IMPACT. HE NOTED THAT THERE WAS A DARK CLOUD BEHIND THE ACFT, LIGHT RAIN WAS FALLING & THE SURFACE WIND WAS FROM THE EAST & WAS GUSTING. THE WINGS, CABIN DOOR & ELEVATOR COUNTERWEIGHTS WERE FOUND ABOUT 1/2 MI WEST OF THE FUSELAGE. THE WINGS HAD FAILED UPWARD, THE VERTICAL STABILIZER HAD SEPARATED AT THE TOP OF THE TAILCONE & THE ENTIRE TAILCONE HAD BROKEN FROM THE FUSELAGE. NO PREEXISTING CRACKS OR FATIGUE WAS FOUND. THE PLT'S LAST MEDICAL CERTIFICATE WAS DATED 4/6/81.