The bad flooding is because of how steep those areas are. Down in Florida, water takes a while to make its way into the creeks, streams, and rivers. The areas with the most extreme flooding is because entire mountainsides worth of rainfall drains in the span of a couple days.
Eastern TN and western NC also had a ton of rainfall from thunderstorms just before Helene so the ground was already saturated. For reference check out this rain gauge in Asheville.
The rain from Helene didn’t really get to Western NC until the early hours of Friday the 27th. That gauge was already at 10 inches by that time. So really the storm before Helene brought more rain than Helene did. Either the thunderstorm or Helene alone would have been moderate, but manageable flash floods, but the two back to back was insane.
The bad flooding is because of how steep those areas are. Down in Florida, water takes a while to make its way into the creeks, streams, and rivers. The areas with the most extreme flooding is because entire mountainsides worth of rainfall drains in the span of a couple days.
Eastern TN and western NC also had a ton of rainfall from thunderstorms just before Helene so the ground was already saturated. For reference check out this rain gauge in Asheville.
https://waterdata.usgs.gov/monitoring-location/353312082355545/#parameterCode=00045&period=P7D&showMedian=false
The rain from Helene didn’t really get to Western NC until the early hours of Friday the 27th. That gauge was already at 10 inches by that time. So really the storm before Helene brought more rain than Helene did. Either the thunderstorm or Helene alone would have been moderate, but manageable flash floods, but the two back to back was insane.