Largely based on it's predecessor (the Fujita Scale), the Enhanced Fujita Scale became the official scale for ranking tornadoes in February 2007.

As many of you already know, the strength of a tornado isn't actually measured until after the storm has hit! Tornado strength is measured based on the damage it leaves behind, and there
has been many updates made to the original scale.

While the principle scale remains the same, a lot of revisions and enhancements were made to account for variables such as vegetation and building structure.

Read the full report.