The reason: The May 31 storm just didn't do enough damage to achieve a higher Enhanced Fujita (EF) rating. Now weather scientists are asking if the rating system needs an overhaul in the age of mobile Doppler radar and other sophisticated tracking techniques, and some are pressing for a new rating formula that would include measurements of maximum wind speeds.

In 1971, when Ted Fujita introduced the original Fujita (F) scale, it wasn't possible to measure a tornado's winds while they were happening. So he proposed creating after-the-event surveys of a tornado's path and correlating storm damage with the intensity of the wind that created it. Was the surface peeled off a home's roof? That's F1 damage, probably from 73- to