Background
The pilot of N9143B had requested and received a weather briefing prior to departure. The briefing indicated that the area forecast for the planned route predicted thunderstorm activity and cumulonimbus clouds with tops as high as FL450, and that a weather system impacting the Florida Gulf Coast consisted of "looming thunderstorms" in that area. During the flight, the pilot contacted the Enroute Flight Advisory Service (EFAS, commonly referred to as "Flight Watch") for enroute weather advisories. The EFAS advised the pilot of "cells" east of St. Augustine, informed him of Convective SIGMET 05E in effect for southern Florida, and recommended a routing toward the Tampa/St. Petersburg area and then southward to avoid an area of thunderstorms.
The Deviation Attempt
At some point during the flight, the pilot asked the controller if he could deviate about 12 miles west, because he thought he saw "a hole" in the weather. Radar ground track plots showed that the pilot had observed a 3-to-5-mile gap between two thunderstorm clusters and attempted to fly through an area of light radar echoes between the two larger areas of heavier echoes. However, radar data indicated that a cluster of thunderstorms, level three to four, was present in the vicinity of N9143B's ground track position at that time.
Loss of Control and Breakup
Radar data showed that N9143B departed level flight and began an uncontrolled descent from FL260 (approximately 27,500 feet mean sea level). Witnesses reported hearing the engine make a winding noise, then observed the airplane emerge from the clouds about 300 feet above the ground, in a nose-low spiral, and the right wing was missing. The right wing was not found at the crash site but was located 1.62 miles from the main wreckage.