Measuring The Power Of Deadly Tornadoes

John Warner surveys the damage near a friend's mobile home in the Steelman Estates Mobile Home Park, destroyed in Sunday's tornado, near Shawnee, Okla., on Monday.

Sue Ogrocki/AP

John Warner surveys the damage near a friend's mobile home in the Steelman Estates Mobile Home Park, destroyed in Sunday's tornado, near Shawnee, Okla., on Monday.

Sue Ogrocki/AP

Damaging tornadoes ripped through Oklahoma on Sunday and Monday, causing widespread damage that is still being assessed, and additional severe weather is expected.

One of the hardest hit areas, Moore, Okla., is no stranger to devastating twisters. A massive tornado that hit on May 3, 1999, 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 National Weather Service.

Tornado strength is currently measured on what is called the Enhanced Fujita Scale (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 Weather Underground:

The Enhanced Fujita Scale

• EF-0 (wind speeds 65-85 mph): Light damage. 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): Moderate damage. 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): Considerable damage. 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): Severe damage. 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): Devastating damage. Well-constructed houses and whole frame houses completely leveled; cars thrown and small missiles generated.
• EF-5 (wind speeds >200 mph): Incredible damage. 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.

Source: http://www.npr.org/blogs/thetwo-way/2013/05/20/185610261/measuring-the-power-of-deadly-tornadoes?ft=1&f=1007

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