They say it may be historic, possibly on a par with the "super outbreak" of April 1974, when 148 tornados in 13 states killed 335 people:
Veteran tornado watchers saw Wednesday's mega-twisters coming.
But they were still staggered by the destruction that a massive storm system unleashed across the Southeast that leveled broad swaths of Tuscaloosa, Ala., and killed more than 280 people.
"I've been at this for a while, and I've never seen anything like this," said Chris Weiss, an associate professor of atmospheric science at Texas Tech University in Lubbock, Tex.
Some of Wednesday's tornadoes could have traveled dozens, or perhaps even hundreds, of miles before eventually dissipating. Typical twisters survive only minutes. Based on early observations, a few of the twisters probably were more than a mile wide, Weiss said.
As of Thursday evening, there had been 173 reports of twisters touching down in the U.S. on Wednesday, said Greg Carbin, warning coordination meteorologist for the National Weather Service's Storm Prediction Center in Norman, Okla.
That number of reports might be typical for an entire April, he said. This year's national preliminary tornado estimate for April has already hit 600, with several days left to go.
"We will finish out with more in this April than in any month we've seen in the last 60 years," Carbin said. "It's really hard, even for me, to get my mind around that number."
[...] This year, the winds from the Gulf of Mexico have been "exceptionally warm and humid for this early in the spring," Ostro said. Those warm winds from the south blew close to the ground this week while a very strong jet stream came in from the west higher up.