On February 1st of this year, the National Weather Service will adopt the new Enhanced Fujita scale for rating tornadoes. The major change is in the wind speeds associated with the F3 and higher ratings. In effect, the same damage will essentially result in the same rating, it is just that the winds associated with each rating will change.
Original FScale
F0 40-72 mph
F1 73-112 mph
F2 113-157 mph
F3 158-206 mph
F4 207-260 mph
F5 261-318 mph
New Enhanced FScale
EF0 65-85 mph
EF1 86-110 mph
EF2 111-135 mph
EF3 136-165 mph
EF4 166-200 mph
EF5 over 200 mph
One clear objective in developing the Enhanced Fujita Scale was that results from the new scale must conform to the ratings already in the tornado database. It became apparent after the Moore, Oklahoma tornado in May 1999 that the wind speeds associated with the original Fujita scale were too high. In other words, the damage was being caused by wind speeds that were lower that the ratings indicated.
Here is a link to the parameters of the Enhanced F Scale for tornado damage:
