Damaging tornadoes
, causing widespread damage that is still being assessed, and additional severe weather is expected.
One of the hardest hit areas, Moore, Okla., is
. A massive tornado that
, was one of the most powerful and destructive single tornadoes in history until the 2011 tornado that hit Joplin, Mo., killing 158 people and causing an estimated $2.8 billion in damage.
Monday's tornado, which is estimated to have been on the ground for nearly 40 minutes and possibly more than a mile wide, followed closely the track of the one that struck in 1999, according to the
.
Tornado strength is currently measured on what is called the
(adapted from the simpler Fujita Scale in 2007), which gives the tornado a rating from 0 to 5 based on estimated wind speeds and the severity of the damage. The 1999 Moore tornado is listed as an F-5, the most powerful, though it is still unclear where on the scale Monday's tornado will be until the damage can be examined.
Below is a quick rundown of the EF scale and damage estimates, according to
:
The Enhanced Fujita Scale
EF-0 (wind speeds 65-85 mph): . Peels surface off some roofs; some damage to gutters or siding; branches broken off trees; shallow-rooted trees pushed over.
EF-1 (wind speeds 86-110 mph): . Roofs severely stripped; mobile homes overturned or badly damaged; loss of exterior doors; windows and other glass broken.
EF-2 (wind speeds 111-135 mph): . Roofs torn off well-constructed houses; foundations of frame homes shifted; mobile homes completely destroyed; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.
EF-3 (wind speeds 136-165 mph): . Entire stories of well-constructed houses destroyed; severe damage to large buildings such as shopping malls; trains overturned; trees debarked; heavy cars lifted off the ground and thrown; structures with weak foundations blown away some distance.
EF-4 (wind speeds 166-200 mph): . Well-constructed houses and whole frame houses completely leveled; cars thrown and small missiles generated.
EF-5 (wind speeds >200 mph): . Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of over 100 yards; high-rise buildings have significant structural deformation; incredible phenomena will occur.
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