Image: A doll among tornado rubble
Jim R. Bounds  /  AP
A doll hangs in a bush at a home in Colerain, N.C., on Monday after a tornado ripped through the area Saturday.
By AP Science Writer
updated 4/18/2011 7:10:29 PM ET 2011-04-18T23:10:29

The devastation is stunning — homes and lives shattered as the deadliest swarm of twisters in three years battered up to 15 states.

Ultimately, this could turn out to be among the top 10 three-day outbreaks for number of tornadoes, though experts can't be sure until all the reports are sorted, said Greg Carbin of the federal Storm Prediction Center in Norman, Okla.

Story: Like 'The Wizard of Oz': South surveys damage from killer twisters

While tornadoes occur regularly, their power always shocks.

This time it was storms battering their way from Oklahoma to North Carolina, claiming at least 44 lives, almost half of those in North Carolina. It was the deadliest since Feb. 5, 2008, when 57 died in the "Super Tuesday" election day tornadoes in the Southeast. And that was the highest tornado death toll since 76 died in 1985.

"A major storm system like this is going to happen every few years, usually in April or May," said Carbin.

While May is the nation's busiest month for twisters, they surge sharply in April, and most early spring tornadoes strike the Southeast and South Central states.

Indeed, the biggest tornado outbreak on record occurred April 3-4, 1974 when 147 confirmed twisters touched down in 13 states, claiming 310 lives in the United States and 8 in Canada.

Story: Tales of survival amid NC tornado destruction

For about the past 30 years, the United States has averaged 135 tornadoes in April, the highest number being 266 in 1974, according to Jake Crouch of the National Climatic Data Center in Asheville, N.C.

Many reports likely duplicates
In these latest storms, the National Weather Service is investigating 267 preliminary tornado reports — including 97 in North Carolina on Saturday. But many of those will turn out to be duplicates, Carbin said in a telephone interview

Such a large number of reports has become typical in recent years as more people watch for the storms and call them in. Normally more than half turn out to be duplicates and Carbin estimated that the final count for this series of storms will be around 140.

Teams are out assessing the damage now, but he said it can take several days to more than a week to make a final determination.

In this case, the storm system first developed over the Pacific and intensified when it got to the central Plains on Thursday where the dry western air collided with the warm humid air from the Gulf of Mexico.

Interactive: 2011 tornado season (on this page)

From there, the storms developed "pretty much as expected" over Oklahoma, Carbin said. Overnight, the storms merged into a fast-moving front crossing Arkansas and into the Mississippi River Valley, drawing fuel from daytime heating, striking on into Mississippi and Alabama and then into the Appalachians by Saturday morning. Then the storms again strengthened with daytime heat for the third day of tornadoes, hitting North Carolina hardest.

Tornado Alley
It's that intersection of dry and wet air masses that sets up Tornado Alley, the region in the center of the country regularly pummeled by tornadoes.

Overall, from Thursday through Saturday, there were reports of funnel clouds in Kansas, Oklahoma, Texas, Arkansas, Alabama, Illinois, Missouri, Mississippi, Kentucky, Georgia, Louisiana, Maryland, Virginia, North Carolina and South Carolina.

April's reputation as a deadly month was cemented in 1936 when a twister killed 216 people in Mississippi on April 5, and a day later another 203 died in Georgia. And 143 people died in Louisiana and Mississippi April 25, 1908.

Recent years tend to be marked by more tornadoes and fewer deaths, as forecasts have improved, along with communications, allowing people to prepare and also encouraging people to report funnel clouds to authorities.

Unlike tornado outbreaks of the past, the National Weather Service reports that nearly 90 percent of the past weekend's reported storms occurred in areas where tornado warnings were in effect. In central North Carolina, 97 percent of the tornadoes were in areas where warnings had been issued, with an average lead time of almost 26 minutes.

By contrast, before 1950 the use of the term tornado in forecasts was discouraged because of a fear that predicting them would cause panic. The first successful tornado forecast was made by Air Force meteorologists at Tinker Air Force Base in Oklahoma in 1948.

Copyright 2011 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Video: Storm survivor: 'It was madness'

  1. Closed captioning of: Storm survivor: 'It was madness'

    >> path barrelled and rolled across the country from the plain states to the deep south . it spread a lot of disaster. there were a number of close calls, weather channel meteorologist jeff morrow is also with us tonight from north carolina . jeff, i watched your coverage all weekend long. an incredible intensity of weather.

    >> reporter: yeah, brian . reports of 240 tornadoes have investigators scrambling. they've already confirmed 150 tornadoes. to put that into context, we typically see 163 tornadoes for the entire month of april. the rampage went on for days, terrifying tornadoes touched down in 15 states. the harrowing moments caught on tape.

    >> we got two, three. oh.

    >> reporter: thursday tushka, oklahoma, not one but several twisters violently spin around each other.

    >> oh, my god. this is not good, guys.

    >> reporter: friday, clinton, mississippi, a tornado works across an overpass and blue power flashes light up the sky .

    >> there goes the roof off the house.

    >> reporter: saturday wilson, north carolina , a walgreens store is ripped to shreds. zee

    >> that's a walgreens exploding.

    >> reporter: it's the deadliest outbreak in the u.s. in three years. at least 44 deaths in six states. all the ingredients come together to create the perfect storm . in this case a big upper air disturbance in the jet steam.

    >> is came charging east-southeast and met up with moist air in the gulf of mexico .

    >> in gloucester, virginia, he barely escaped.

    >> it sounded like a train was coming to hit the house.

    >> wow.

    >> reporter: in raleigh, north carolina this car still has its lights on and its beeping.

    >> this person must have got out of the car fast. you can hear it .t

    >> the tornadoes were moving very fast in this case. you had little time to seek shelter.

    >> reporter: in boones chapel, alabama the tornado that hit this small town packed 150-mile-per-hour winds. in hard-hit north carolina at least five tornadoes reached similar wind speeds , and that tornado that hit the lowe's traveled more than 60 miles on a fast and brutal path. and, brian , it doesn't look like the nation will get a chance to catch its breath severe weatherwise. they already have a moderate risk of severe weather including the possibility of more tornados from oklahoma to arkansas into the ohio valley for tomorrow and tomorrow night. brian .

    >> jeff morrow , the weather channel , with us from north carolina tonight. jeff, thanks for that.

Photos: Dozens dead after storms rip through 6 states

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  1. Dade County High School student Marcella Lackey, second left, dances with Craig Holmes, left, at her high school prom in Dade County, Ga., on Saturday, May 14. Two weeks after a tornado devastated their town, students from Dade County High came together for their prom, hoping the traditional teenage rite of passage can help them regain a sense of normalcy. (Billy Weeks / AP) Back to slideshow navigation
  2. An aerial photo taken on April 17 shows a home severely damaged by a tornado that ripped through Gloucester, Va. on April 16. Tornadoes and flash flooding have left several people dead in Virginia, and crews are continuing to assess damage that severe weekend storms caused across several areas of the state. (Randall Greenwell / The Virginian-Pilot via AP) Back to slideshow navigation
  3. Tornado victim Clay Anderson, left, with his dog Mindy, sits on the steps of his back porch and talks with American Red Cross volunteer Kathi Garrett in the Saint Andrews community in Sanford, N.C. on April 17. (Wesley Beeson / The Sanford Herald via AP) Back to slideshow navigation
  4. Nathaniel Ramey, left, comforts Megan Hurst at her grandmother's house in Askewville, N.C. on April 17 after a tornado struck the previous day. (Jim R. Bounds / AP) Back to slideshow navigation
  5. This aerial photo taken on April 17 shows a home severely damaged by a tornado that ripped through Gloucester, Va. on April 16. (Randall Greenwell / AP) Back to slideshow navigation
  6. Kathy Gay looks up at the damaged ceiling in the home of her brother Gary Jordan on April 17 in Gloucester, Va. (Steve Earley / The Virginian-Pilot via AP) Back to slideshow navigation
  7. A car is swallowed up by a hole left after a tree fell as a tornado passed just south of downtown Raleigh, N.C. on April 17. (Stan Gilliland / EPA) Back to slideshow navigation
  8. The remains of two school buses at Page Middle School in Gloucester, Va. on April 17, a day after the tornado hit. (Steve Earley / The Virginian-Pilot via AP) Back to slideshow navigation
  9. Chris Nelson hugs his daughter Andrea, 15, in the parking lot in front of Lowe's hardware store in Sanford, N.C. on April 17, a day after a tornado destroyed the building while the Nelsons were inside shopping. The Nelsons returned Sunday to reclaim their truck, back right. (Ted Richardson / AP) Back to slideshow navigation
  10. An aerial photo shows tornado damage at the Lowe's Home Improvement Center in Sanford, N.C. on April 17. (Thomas Babb / AP) Back to slideshow navigation
  11. Mary Grady sits in her neighbor's yard where she rode out a tornado in Askewville, N.C. on April 17. Her home was destroyed in the storm. (Jim R. Bounds / AP) Back to slideshow navigation
  12. A woman inspects her home and car in Raleigh, N.C. on April 17, after homes and businesses were badly damaged Saturday by a severe storm system that whipped across the state. It brought flash floods, hail and reports of tornadoes from the western hills to the streets of Raleigh. (Jim R. Bounds / AP) Back to slideshow navigation
  13. Debris fill the street after a tornado hit Raleigh, N.C., April 17. Tornadoes tore through the Carolinas on Saturday afternoon as the death toll rose to at least 45 people from the storms across the southern United States over the last three days. (Chris Keane / Reuters) Back to slideshow navigation
  14. Raleigh police officer J.L. Bloodworth speaks with a man seeking information about relatives who live at the Stoney Brook Mobile Home Park in Raleigh, N.C., Saturday, April 16, where three people where killed. (Jim R. Bounds / AP) Back to slideshow navigation
  15. A worker takes a picture of the damage left behind by a tornado in Raleigh, N.C. (Chris Keane / Reuters) Back to slideshow navigation
  16. Jeffrey Tan, 13, left, sits on the tree that fell on his great-grandmother's house, Saturday, April 16, in Raleigh, N.C. (Chris Seward / AP) Back to slideshow navigation
  17. An auto repair shop lost its back wall and roof after a tornado ripped through the area, Saturday, April 16, in Raleigh, N.C. (Robert Willett / AP) Back to slideshow navigation
  18. Emergency personnel confer in front of Lowe's Home Improvement after it was hit by a tornado in Sanford, N.C., Saturday, April 16. "The Lowe's Home Improvement has been flattened," said Monica Elliott, who works at the nearby Brick City Grill. "It's totally destroyed." (Jim R. Bounds / AP) Back to slideshow navigation
  19. A.C. Bivens looks at the damage to his home after a tornado ripped through Washington County, Ala., on April 16. (Dan Anderson / EPA) Back to slideshow navigation
  20. Family and friends go through the debris of what is left of Gene Box's trailer after a tornado killed her and two of her children while ripping through Washington County, Ala., on April 16. (Dan Anderson / EPA) Back to slideshow navigation
  21. Only stairs and flowers remain Saturday, April 16, after severe winds tore a mobile home off its lot late Friday night in Boone's Chapel, Ala. (Amanda Sowards / Montgomery Advertiser via AP) Back to slideshow navigation
  22. Bill Mosley, right, urges his daughter Lisa Mosley to walk carefully through the spare bedroom, fearful that she step on a roofing nail as the two gather possessions from the tornado damaged house in Clinton, Miss., Friday, April 15. (Rogelio V. Solis / AP) Back to slideshow navigation
  23. Standing amid downed trees and destroyed houses, members of Southside Baptist Church of Yazoo City, give a prayer of thanks following several hours of work cutting up trees and removing storm debris in this Clinton, Miss., neighborhood, Friday, April 15. (Rogelio V. Solis / AP) Back to slideshow navigation
  24. A car drives through a partially flooded street, Friday, April 15, 2011 in Decatur, Ala. (John Godbey / The Decatur Daily via AP) Back to slideshow navigation
  25. Storms continue to brew as I-20 is shut down after a morning tornado downed power lines and overturned cars and trucks Friday, April 15, in Clinton, Miss. (Brian Albert Broom / AP) Back to slideshow navigation
  26. Friends and neighbors help tornado stricken residents remove possessions in east Clinton, Miss., Friday, April 15. (Rogelio V. Solis / AP) Back to slideshow navigation
  27. A billboard lays collapsed on the ground after a tornado went through Friday, April 15, in Tuscaloosa, Ala. (Michelle Lepianka Carter / The Tuscaloosa News via AP) Back to slideshow navigation
  28. Makala Welch helps her grandparents clean up after a tornado touched down in Clinton, Miss., April 15. (Charles Smith / AP) Back to slideshow navigation
  29. Jerome Whittington attempts to salvage belongings through the window of his automobile in Tushka, Okla., Friday, April 15. (Sue Ogrocki / AP) Back to slideshow navigation
  30. Two women stand in the middle of what used to be houses after a large tornado hit the small town of 350 people, killing two, in Tushka, Okla., April 15. (Larry W. Smith / EPA) Back to slideshow navigation
  31. A woman removes belongings from a house damaged after a large tornado hit Tushka, Okla., April 15. (Larry W. Smith / EPA) Back to slideshow navigation
  32. Evan Whitehead walks past a family member's vehicle and house while looking for belongings after a large tornado hit Tushka, Okla., April 15. (Larry W. Smith / EPA) Back to slideshow navigation
  33. Volunteers pitch in to remove branches from a fallen oak tree in Tushka, Okla., Friday, April 15, following a tornado. (Sue Ogrocki / AP) Back to slideshow navigation
  34. Denym Pingleton, left, carries her books out of the inside of what is left of their school with fellow students Kayla Wilhite, right, and Courtney Wilhite after a large tornado hit Tushka, Okla., April 15. (Larry W. Smith / EPA) Back to slideshow navigation
  35. A severe storm passes over east Tulsa and the Renaissance Hotel, in Tulsa, Okla., April 14. (James Gibbard / Tulsa World via AP) Back to slideshow navigation
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Interactive: Birth of a tornado

  1. Above: Interactive Birth of a tornado
  2. Interactive 2011 tornado season

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