Helene produced such a large amount of rainfall due in part to a predecessor event, small (relative to a hurricane) regions of heavy rainfall produced ahead of a hurricane. These rainfalls produce a band of "deep tropical moisture" which, when mixed with a hurricane, cause significant rainfall.

Instead, the hurricane cut a path up the U.S., causing record breaking flooding in areas like Tennessee and North Carolina, and devastating mountain towns like Asheville, N.C. The catastrophic damage and loss of life — as of Sept.