The Washington Post just released new findings from the Center for Severe Weather Research regarding "ribbon" features embedded within tornadic thunderstorms.
VORTEX2 is the massive tornado research project that is investigating the processes responsible for spinning up tornadoes. While meteorologists know the general ingredients necessary for producing tornadoes, they have yet to discover why one thunderstorm will produce a tornado while another storm will not.
Data from the VORTEX2 project suggests that a ribbon of light rain and small rain drops develops within tornadic thunderstorms.
Josh Wurman, founder of the Center for Severe Weather Research, noted that "we don’t know why it forms or whether it is important in tornado genesis... It is probably present in lots of supercells, but, frankly, we won’t know until we look some more. We’re publishing our initial imagery of this newly discovered phenomenon in the hope that scientists will start pondering why it forms and whether it is important.”