Joplin tornado May 22, 2011

In this photo taken Monday, May 7, 2012, Mark Norton places flowers on the Webb City, Mo., grave of his son Will Norton, who died a year ago when he was sucked out of his car on the way home from his high school graduation by an EF-5 tornado that tore through Joplin, Mo. nearly a year ago. (AP Photo/Charlie Riedel)

In this photo taken Tuesday, May 8, 2012, a tattered flag shows a years worth of wear as it hangs from the remains of a destroyed home in Joplin, Mo. Reconstruction continues in the community as the anniversary of an EF-5 tornado that destroyed a large swath of the city and killed 161 people approaches on May, 22. (AP Photo/Charlie Riedel)

In this photo taken Tuesday, May 8, 2012, a new home rises among ruins of others in a Joplin, Mo., neighborhood which was destroyed by an EF-5 tornado nearly a year ago. Reconstruction continues in the community as the anniversary of the costliest tornado on record approaches on May, 22. (AP Photo/Charlie Riedel)

In this photo taken Tuesday, May 8, 2012, groundwork is done for the new Mercy Hospital Joplin a couple miles south of the former St. John's Regional Medical center it replaces in Joplin, Mo. Destroyed by an EF-5 tornado nearly a year ago, the hospital is in its third temporary facility while construction continues on the new building. (AP Photo/Charlie Riedel)

Renee Denton, director for medical oncology and pediatrics at Freeman Hospital, releases a lantern Tuesday, May 22, 2012 during Morning Has Broken event at Freeman Hospital. The laterns were in remembrance of the May 22, 2011 tornado victims. The tornado killed 161 people and destroyed one-third of the city, making it the nation's deadliest single tornado in six decades. (AP Photo/The Joplin Globe, Roger Nomer)

In this photo taken May 8, 2012, Maggie Ward, 7, plays in a monument to volunteers at a Joplin, Mo., park across the street from the former St. John's Regional Medical center. The park and hospital were both destroyed after an EF-5 tornado tore through a large swath of the city nearly a year ago. (AP Photo/Charlie Riedel)

In this photo taken Tuesday, May 8, 2012, the ruins of the former St. John's Regional Medical center stands in Joplin, Mo. Destroyed by an EF-5 tornado nearly a year ago, the hospital is in its third temporary facility while construction continues on a new replacement a couple miles to the south. (AP Photo/Charlie Riedel)

In this photo taken Tuesday, May 8, 2012, groundwork is done for the new Mercy Hospital Joplin a couple miles south of the former St. John's Regional Medical center it replaces in Joplin, Mo. Destroyed by an EF-5 tornado nearly a year ago, the hospital is in its third temporary facility while construction continues on the new building. (AP Photo/Charlie Riedel)

In this photo taken Tuesday, May 8, 2012, Hollyhocks grow in an abandoned garden at a destroyed home in Joplin, Mo. Reconstruction continues in the community as the anniversary of an EF-5 tornado that destroyed a large swath of the city and killed 161 people approaches on May, 22. (AP Photo/Charlie Riedel)

President Barack Obama speaks at the Joplin High School commencement ceremony, Monday, May 21, 2012, at Missouri Southern State University in Joplin, Mo. (AP Photo/Charlie Riedel)

President Barack Obama delivers the Joplin High School commencement address a day before the anniversary of the twister that killed 161 people, Monday, May 21, 2012, in Joplin, Mo. Obama jetted to Joplin immediately after wrapping up the national security-focused NATO conference in Chicago, the second international summit the president hosted over the past four days. (AP Photo/The Kansas City Star, Shane Keyser)

President Barack Obama, center, with Missouri Gov. Jay Nixon, left, and Superintendent C.J. Huff, right, applaud the Class of 2012 at the Joplin High School commencement ceremony, Monday, May 21, 2012 at Missouri Southern State University in Joplin, Mo. (AP Photo/Pablo Martinez Monsivais)

Graduating seniors of Joplin High School applaud president Barack Obama after his speech Monday night, May 21, 2012 at commencement exercises in Joplin, Mo. (AP Photo/The Kansas City Star, Rich Sugg, Pool)

President Barack Obama speaks at the Joplin High School commencement ceremony, Monday, May 21, 2012, at Missouri Southern State University in Joplin, Mo. (AP Photo/Pablo Martinez Monsivais)

Chad Efird tosses debris out of a house as he assists with cleanup Tuesday, May 24, 2011, in Joplin, Mo. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Jeff Roberson)

Gary Terry, left, and James Ruddick look through the debris of the auto repair shop they work at in Joplin, Mo., Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. (AP Photo/Mark Schiefelbein)

Amy Gilbert stands just outside the garage after a tornado damaged her house Tuesday, May 24, 2011, in Joplin , Mo. A tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses and killing at least 116 people. Gilbert was at home when a tornado ripped the roof off her house. (AP Photo/Jeff Roberson)

Search and rescue teams fan out across destroyed Joplin neighborhoods on Tuesday morning, May 24, 2011. Rescue crews worked through the rain-soaked chill of night, ignoring lightning and strong winds to dig through splintered homes, crumpled businesses and crushed cars in Joplin. (PAP Photo/Robert Ray)

A torn and muddied American flag flies as employees of a boiler company search through the wreckage of their office on the east side of Joplin, Mo., Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. The workers said the flag was not theirs, but that they had found it in the building's debris, apparently carried there from somewhere else. (AP Photo/Mark Schiefelbein)

Linda Dinwiddie stands outside a tornado-damaged house belonging to her nephew Tuesday, May 24, 2011, in Joplin , Mo. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Jeff Roberson)

A destroyed neighborhood is seen in Joplin, Mo. Tuesday, May 24, 2011. A tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses and killing at least 116 people. (AP Photo/Charlie Riedel)

Members of Missouri Task Force One search-and-rescue team gather a tornado-damaged Home Depot store Tuesday, May 24, 2011, in Joplin , Mo. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Jeff Roberson)

Amy Gilbert, left, gets a hug from her friend Jason Dickinson as they work to clean up Gilbert's tornado-damaged home Tuesday, May 24, 2011, in Joplin , Mo. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Jeff Roberson)

Carla Austin, right, picks through the rubble of her home with the help of friend Jon Derouchey Tuesday, May 24, 2011, in Joplin , Mo. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Jeff Roberson)

Nick Swainston with Oklahoma Task Force One search-and-rescue climbs over debris as he searches for victims on Tuesday, May 24, 2011, in Joplin , Mo. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Jeff Roberson)

Workers remove boards by hand as a bulldozer excavates larger chunks of debris from the wreckage of a Home Depot store in Joplin, Mo., Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. (AP Photo/Mark Schiefelbein)

Workers are lifted into place with a crane to start disassembling a collapsed cell phone tower in Joplin, Mo., Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. (AP Photo/Mark Schiefelbein)

This aerial photograph shows a neighborhood destroyed by a powerful tornado in Joplin, Mo. Tuesday, May 24, 2011. A tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses and killing at least 116 people. (AP Photo/Charlie Riedel)

A torn American flag stands in the wreckage of a church in Joplin, Mo., Tuesday, May 24, 2011. Rescue crews worked through the rain-soaked chill of night, ignoring lightning and strong winds to dig through splintered homes, crumpled businesses and crushed cars in Joplin. (AP Photo/Robert Ray)

Matt Asbill digs through the wreckage of the office of his engineering business on the east side of Joplin, Mo., Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. (AP Photo/Mark Schiefelbein)

A destroyed neighborhood is seen in Joplin, Mo. Tuesday, May 24, 2011. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Charlie Riedel)

Police officers walk in to the back of a destroyed Wal-Mart store in Joplin, Mo., Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. (AP Photo/Mark Schiefelbein)

Brent Koeninger, with Oklahoma Task Force One search-and-rescue, and his search dog Huck comb through debris looking for victims Tuesday, May 24, 2011, in Joplin, Mo. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Jeff Roberson)

A vehicle sits amid the debris of a cell phone tower that collapsed onto an apartment building on the east side of Joplin, Mo., Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. (AP Photo/Mark Schiefelbein)

Tom Flood, 90, searches through the wreckage of his home Tuesday, May 24, 2011, in Joplin , Mo. Flood and his wife, Rose, were not at home when a tornado hit Joplin on Sunday evening. (AP Photo/Jeff Roberson)

Joe Hackett searches for his belongings in the rubble of his third-floor apartment in a complex on the east side of Joplin, Mo., Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. Hackett, who was planning to move to a new home in a week, was not at home when the tornado struck. (AP Photo/Mark Schiefelbein)

A destroyed apartment complex is seen in Joplin, Mo. Tuesday, May 24, 2011. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Charlie Riedel)

Greg Beeching, left, of Carl Junction, Mo., and his son Brian Beeching of Joplin, Mo., move a washer and dryer out of a relative's damaged apartment in Joplin, Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. (AP Photo/Mark Schiefelbein)

Rescue workers gather at a destroyed Home Depot in Joplin, Mo. Tuesday, May 24, 2011. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Charlie Riedel)

Amy Gilbert stands in what is left of her kitchen Tuesday, May 24, 2011, in Joplin , Mo. Gilbert and her husband, Eric, were standing in the kitchen as the roof began to tear away from the house during a tornado Sunday night. The couple was able to seek shelter in a bathroom off the kitchen along with their eight-year-old daughter their dogs and a friend. All survived without injury. (AP Photo/Jeff Roberson)

A keepsake reading "Bless this house" hangs on a cabinet inside Tom and Rose Flood's tornado-damaged house as storm cleanup continues outside Tuesday, May 24, 2011, in Joplin , Mo. The couple was not at home when a tornado struck Sunday night destroying nearly every home in their neighborhood. (AP Photo/Jeff Roberson)

High school jackets belonging to Don Lansaw and his wife, Beth Lansaw, are seen Tuesday, May 24, 2011, in Joplin , Mo. Don Lansaw was killed and his wife injured when a tornado ripped through Joplin on Sunday. (AP Photo/Jeff Roberson)

A destroyed neighborhood is seen in Joplin, Mo. Tuesday, May 24, 2011. A tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses and killing at least 116 people. (AP Photo/Charlie Riedel)

Police officers stand near the location where a possible body was found in the debris of a Home Depot store in Joplin, Mo., Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. (AP Photo/Mark Schiefelbein)

Members of Missouri Task Force One search-and-rescue team work at a tornado-damaged Home Depot store Tuesday, May 24, 2011, in Joplin , Mo. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Jeff Roberson)

Keith Henning and his wife Leslie clear debris from the wreckage of the office where Hening works on the east side of Joplin, Mo., Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. (AP Photo/Mark Schiefelbein)

Oklahoma Task Force One search-and-rescue members, from left, Jim Winham, Nick Swainston and Kevin Mann search through debris for victims on Tuesday, May 24, 2011, in Joplin , Mo. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Jeff Roberson)

A destroyed apartment complex is seen in an aerial view over Joplin, Mo. Tuesday, May 24, 2011. A tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses and killing at least 116 people. (AP Photo/Charlie Riedel)

Beth Lansaw wipes away tears as she stands in the backyard of her son's home Tuesday, May 24, 2011, in Joplin , Mo. Lansaw's son, Don Lansaw, was killed when a tornado hit his home Sunday night. (AP Photo/Jeff Roberson)

A police officer pushes a cart loaded with supplies to a command post behind a destroyed Wal-Mart store in Joplin, Mo., Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. (AP Photo/Mark Schiefelbein)

Residents look at an acoustic guitar while searching through the wreckage of their third-floor apartment on the east side of Joplin, Mo., Tuesday, May 24, 2011. At least 116 people were killed and hundreds more injured when a tornado cut a destructive path through Joplin on Sunday evening. (AP Photo/Mark Schiefelbein)

Members of Missouri Task Force One search-and-rescue team search a tornado-damaged Home Depot store Tuesday, May 24, 2011, in Joplin , Mo. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Jeff Roberson)

Members of Missouri Task Force One search-and-rescue team stand by as heavy equipment moves debris from a tornado-damaged Home Depot store Tuesday, May 24, 2011, in Joplin , Mo. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Jeff Roberson)