More than half of these top-of-the-scale twisters have occurred in just five states: Alabama, Iowa, Kansas, Oklahoma and Texas.
The twisters are part of a severe weather outbreak that is sweeping through the region as storms move east.
Tornado warnings have appeared on the weather service's alerts map early Wednesday, an indication the front may have spawned twisters.
"Yet it was a relatively ordinary violent tornado, " according to Brooks, an acknowledged expert on the climatology and probability of twisters.
Clinton visited there to show his support for the survivors, especially African Americans who have felt neglected in the days since the twisters.
CNN: Clinton Authorizes More Aid For Alabama Tornado Victims
Such twisters are defined as those that have winds of at least 200 mph, are a half-a-mile or more wide, and produce the most fatalities.
The twisters are part of a severe weather outbreak that is sweeping through parts of Kansas, Oklahoma, Iowa and Missouri as the storms sweep east.
Around the Southeast, meanwhile, authorities were investigating several reports of twisters from the system that had raked Missouri and Arkansas on Tuesday before heading eastward.
Around the Southeast, meanwhile, authorities were investigating several reports of twisters.
Dean and seven of his tourists found themselves near El Reno last week on the jam-packed roads when the deadly twisters began to drop from the sky.
Torrential downpours followed for hours after the twisters moved east up to 7 inches of rain in some parts and the city's airport had water damage.
Deaths from twisters have been declining in recent years because of improved forecasts and increased awareness by people living in tornado-prone areas, especially in smaller and rural communities.
The repeat twisters and even seemed to increase their resolve.
While the twisters damaged houses in Missouri and Illinois, the brunt of their force was reserved for Oklahoma City and its surrounding areas, including El Reno and Union City.
"This is fairly weak in terms of tornadoes, but we saw the awesome power of the twisters as they lifted the trailers several hundred feet in the air, " he said.
Clinton also announced other federal measures to help the Alabama towns hit by the twisters, including counseling programs and temporary work for those who lost their jobs due to the storms.
CNN: Clinton Authorizes More Aid For Alabama Tornado Victims
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It followed some of the deadliest tornado outbreaks on record in the U.S. last spring, when 175 twisters ripped across Alabama and other states in April, killing 316 people, and a massive twister struck the Joplin, Mo.
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