In about 15 minutes, Tempe recorded nearly three-quarters of an inch of rain. A supercell thunderstorm forms when wind speed and direction change with height, a phenomenon called wind shear.

Add Yahoo as a preferred source to see more of our stories on Google. A powerful supercell thunderstorm, which triggered a microburst in Tempe, dropped heavy rain across the East Valley Oct. 13, ...

A powerful supercell thunderstorm, which triggered a microburst in Tempe, dropped heavy rain across the East Valley Oct. 13, flooding streets and toppling trees as wind gusts neared 70 mph. In about ...