National Weather Service United States Department of Commerce

Super Tuesday - February 5-6, 2008 Tornado Outbreak


I know a lot of people are probably wondering why the tornado lifted as it approached Davidson County Tuesday Night February 5th, 2008.

I'm not sure that we will ever know the complete answer but here are my thoughts as what may have caused it to lift as it moved through Davidson County.

Over the years there have been a lot of studies of supercell tornadoes and their environment.

One concept that I think could have played a role is that of the Rear Flank Downdraft.


Warm Rear Flank Downdrafts promote tornadoes, while Cold Rear Flank Downdrafts discourage them.

Cold air downbursts impinging upon the tornado as it approached Davidson County would have caused the tornado funnel to tilt increasingly from the vertical, becoming a funnel cloud as it lifted above the ground and possibly dissipating over Davidson County to only reform in Sumner County a short while later as warmer air got entrained.

Spotter reports of strong, warm inflow winds Southeast of the wall cloud (area of strongest updraft) would suggest a higher tornado risk than the case where the wall cloud is undercut by cold air outflow.

Bobby Boyd
NWS/Nashville, TN