Radar sweeps after the rocket's failure captured the thick cloud of smoke traveling up the coast after the explosion. The returns are so strong on radar that the smoke and fumes look like a thunderstorm:
Weather radar detects precipitation by sending out a beam of microwave energy and reading how much of that energy was returned to the radar site. Anything that's able to reflect this beam back to the radar site registers as a return, which is why radar is able to detect non-precipitation events such as birds, bugs, tornado debris, and even the debris field left behind when Space Shuttle Columbia broke up on reentry in February 2003.
[Images: Gibson Ridge]