Charlie Riedel / AP

A man salvages a guitar from a severely damaged home in Joplin, Mo., on May 23, 2011.

While Oklahoma begins to clean up after a ferocious tornado, the site of one of the worst twisters in American history — Joplin, Mo., a little more than 200 miles away — marked a solemn anniversary Wednesday.

On May 22, 2011, a tornado all but wiped Joplin off the map. The twister killed 161 people, injured more than 1,000 and wrought almost $3 billion worth of damage. It was clocked at more than 200 mph.

But the town has come back even stronger with changes to their infrastructure that are helping people stay safe. Now, nearly 80 percent of new homes include a safe room, and a new hospital will open in 2015 with windows able to withstand 250 mph winds.

“Devastation is a short walk, but determination lasts all the time,” Mayor Melodee Colbert Kean said. “Joplin is a city of hope. We know what it’s like to suffer… but know what it's like to get back up.”

Ninety percent of affected businesses are now open and 75 percent of the homes have been rebuilt.

And Mercy Hospital, once the symbol of the tornado's fury, was running again in just eight months.

A new facility will open in 2015 with walls and windows built to withstand 250 mph winds and its electrical systems securely buried under ground.

A moment of silence was held at 5:41 p.m. local time, the moment the tornado struck two years ago. Homeland Security Secretary Janet Napolitano, who earlier in the day was in Moore, Okla., to pledge federal help, attended the commemoration.

Joplin sent a support team to Moore to help with the recovery. The cities each have about 50,000 people.

The Joplin tornado damaged or destroyed 7,500 homes. On the Senate floor Wednesday, Missouri Sen. Roy Blunt said there were lessons for Moore in the rebuilding.

“For the people in Joplin, they immediately began to think about Joplin tomorrow instead of Joplin yesterday,” he said. “And two years later, it’s still a community that’s dealing with loss, but a community that’s building new schools and new businesses.”

The Federal Emergency Management Agency provided housing for 586 households after the Joplin tornado, and all but 12 have moved into longer-term or permanent homes, the city says.

NBC News' Becky Bratu contributed to this report.

Slideshow: Tornadoes ravage Plains

Tannen Maury / EPA

A monster tornado hit Moore, Okla., Monday afternoon, leaving at least 24 dead.

Launch slideshow

This story was originally published on Wed May 22, 2013 7:22 PM EDT

Paul Hellstern/The Oklahoman, NewsOk.com

Teachers carry children away from Briarwood Elementary school in Moore, Okla., after a tornado destroyed the school Monday.

Heroic action was in no short supply Monday as a massive tornado blazed a trail of destruction through Moore, Okla.

Did you witness ordinary people doing extraordinary things? Share your stories, photos and video with us by email, or on Twitter using hashtag #OKheroes -- but only if it is safe to do so. Selected responses may be used in an upcoming story.

Evening Standard

London's Evening Standard newspaper reports on the tornado in Oklahoma.

Pope Francis and Britain’s queen sent messages of condolence to those affected by the deadly Oklahoma tornado Tuesday, as news of the devastation spread around the world.

"I am close to the families of all who died in the Oklahoma tornado, especially those who lost young children,” the pontiff posted on his Twitter feed. “Join me in praying for them."

The U.S. Embassy in London thanked British well-wishers for their expressions of support.

In a statement issued by Buckingham Palace officials, Queen Elizabeth said: "I was deeply saddened to hear of the loss of life and devastation caused by yesterday’s tornado in Oklahoma."

"Prince Philip joins me in offering our heartfelt condolences to the victims and their families at this difficult time. Our deepest sympathies go out to all those whose lives have been affected, as well as the American people," she added.

Canada's foreign minister John Baird said he was "shocked and saddened" at the devastation.

"Canada stands with those affected, ready to assist," he added.

Pakistan’s Ministry of Foreign Affairs said in a statement that the government and people of the country were “deeply saddened and shocked at the humanitarian tragedy unleashed on the Oklahoma State by a devastating tornado.”

“Our sympathies and prayers go out to the families of victims of this horrific incident that led to precious loss of life and property,” the statement said. “We are particularly grieved over the loss of innocent children and their teachers who were buried under the rubble.”

“May God Almighty give courage and strength to the bereaved families to bear this irreparable loss. The people of Pakistan stand hand in hand with the people of Oklahoma at this difficult time,” it added.

Full coverage of the Oklahoma tornadoes from NBC News

This story was originally published on Tue May 21, 2013 9:01 AM EDT

Sue Ogrocki / AP

A child calls to his father after being pulled from the rubble of the Plaza Towers Elementary School in Moore, Okla., on Monday.

When the sirens began blaring and teachers at Plaza Towers Elementary School in Moore, Okla., heard that a monstrous tornado was roaring toward their 57-year-old school and its youngest students, there was nowhere to hide.

They crouched in hallways and bathrooms, waiting, hoping and praying. Then "the school started coming apart," one neighbor who sought shelter at the school told the Associated Press. A teacher told NBC station KFOR that she draped herself on top of six children in a bathroom to shelter them.

The massive twister scored a direct hit at 3 p.m. (4 p.m. ET), tearing off the roof of the mostly one-story public school, a cinder-block building that had no chance of withstanding shrieking winds that may have topped 200 mph -- the powerful outer edge of what the National Weather Service said was at least an EF4 tornado, the second-most-powerful rating.

By Tuesday morning, the death toll at the school stood at seven. Officials said the children drowned in a pool of water at the decimated school. Rescuers were continuing to dig through the school’s rubble, from which several children were pulled out alive Monday evening.

It's unclear if any other children were killed or trapped alive.

Hysterical parents who had converged on the sprawling pile of broken concrete and twisted metal were later taken to a church to await word on the fate of their youngsters.

The two-mile-wide tornado wiped out entire city blocks of Moore, the hardest-hit Oklahoma City suburb, killing at least 24 people, the state medical examiner office confirmed. Many of the dead are children.

Exactly what transpired at Plaza Towers in the minutes before the tornado unleashed its destructive power has yet to be described. School officials evacuated fourth-, fifth- and sixth-graders to a church about a quarter-mile away before it touched down, but the younger students – kindergartners through third graders – remained at the 440-student school, according to KFOR in Oklahoma City. It was not immediately known why school officials divided the students.

Bing (top) | AP (bottom)

Before and after aerial photos of Plaza Towers Elementary School.

But Mayer Nudell, a security and safety consultant, did not fault the decision to ride out the storm at the school.

“For something like a tornado, it’s fairly academic,” he said of the options that school officials would have had once the sirens began. “You don’t go out, and you don’t have much warning.”

Despite the carnage at the school, “shelter in place” has emerged as a staple of disaster planning and the strategy of choice for a range of emergencies, including tornadoes. And studies show it has a good track record of saving lives.

On May 3, 1999, for example, when another monster tornado roared through Moore, some 300 students and their parents were attending an awards ceremony in the West Moore High School auditorium. Though the twister badly damaged the school and tossed 150 cars in the parking lot like tinker-toys, those who hunkered down in the school’s hallways suffered only a few superficial injuries.

But there are experts who say that having a large number of people crowded into a big building is a bad idea when maximum-force tornadoes are sweeping through an area.

Chief among them is Joe R. Eagleman, a professor emeritus of the University of Kansas and author of “Severe and Unusual Weather,” a meteorology standard since it was first published in 1983.

He agrees that there was likely insufficient time between the first warning and the time the tornado hit the school, constructed in 1966, for Plaza Towers administrators to consider sending students home. “If time is short, being caught out in the open is not good,” he said.

But he said dispersing the students to their homes would have improved their odds.

“If there is sufficient warning time, the homes would be typically safer because they are smaller buildings and offer more opportunity to get in a downwind corner of the likely approach,” he said.

Eagleman is widely credited with debunking what was the prevailing school of thought on tornadoes for much of the last century: that the safest spot to take shelter is the southwest corner of a building. The reasoning behind the fallacy was that, since most U.S. tornadoes travel from west-southwest to the east-northeast, a twister would hurl debris into the northeast corner of whatever building it hit, likely taking out anyone cowering there.

But Eagleman conducted an extensive study after an EF5 tornado hit Topeka, Kan., in 1966, and found that the southwest corner – the direction from which a tornado was most likely to approach – was in fact the most dangerous area to hide.

“It used to be a rule that the southwest corner was the safest, no questions asked, but it was not based on any data,” he said.

Once Plaza Towers officials made the decision to have the students and teachers shelter in place, the school’s disaster plan would have kicked in. The staff and student body would likely have been well-coached, given the school’s location in “Tornado Alley” and Moore’s history of destructive tornadoes, though Eagleman noted that “it varies all over the place as to what the planning has been for severe storms.”

In any case, students would have been moved into a hallway or small room away from the southwest corner of the building and any windows and instructed to either sit or crouch.

“You want a place that is structurally secure, without windows, so you don’t have to worry about flying glass,” said Nudell, who also is an adjunct professor of security management at Webster University in Webster Groves, Mo., and co-author of “The Handbook for Effective Emergency and Crisis Management.”

Both men said the school’s construction would have been important to its ability to withstand a powerful twister.

“The buildings that are made of reinforced concrete are typically very sturdy,” Eagleman said. “Those made with concrete blocks are not.”

But given the destruction visible after the tornado swept through Moore, it’s possible that no building would have withstood the intense pressure that the tornado brought to bear on the building, Nudell said.

Nudell also cautioned against jumping to conclusions about the emergency planning or safety of the school.

“When you get a tornado like the one that it sounds like hit Oklahoma, sometimes all the preparation and planning in the world doesn’t help you,” he said.

NBC News' Erin McClam and Tracy Connor contributed to this report.

Related stories: 

• Monster tornado tears through Oklahoma
• Six of the worst tornadoes in US history
• Full coverage of Oklahoma tornadoes from NBC News

Survivors of the tornadoes that devastated two towns in Texas on Wednesday night described their terror as the violent storm tore apart their homes, killing six people and injuring dozens more.

The last of those believed to be missing have been accounted for in the hard-hit Hood County town of Granbury, where a cluster of more than 60 homes built by Habitat for Humanity were among the worst off.

The Zapata family took refuge in the bathtub of their Granbury home as the twisters approached on Wednesday.

“I couldn’t stop screaming or crying,” Ana Zapata, 18, said of how she sheltered with her parents and two siblings under a pair of mattresses.

Full coverage from NBCDFW.com

“Feeling the walls shake and the tub under you is feeling like it is going to lift up any time,” her father Paul Zapata told KXAS. “Thank God we’re here, we’re alive.”

Joseph Youngblood, 10, was playing outside of a friend’s house in Granbury when the sirens went off. The skies darkened ahead of what the weather service said was an EF-4 tornado, meaning it packed winds of between 160 and 200 miles per hour.

“We started hearing the tornado sirens go off and then we look up at the clouds and we see the tornado twisting, so we all rushed in the bathroom,” Youngblood said. “I just went and ducked somewhere. I didn’t even care. I was so scared.”

The boy took refuge with his friend’s family in their house’s bathroom, where his friend’s father struggled to hold the bathroom door closed against the powerful winds that were collapsing the house around them.

"[The tornado] was starting to get more power and then he was, like, barely hanging on because the tornado was about to suck him outside," Youngblood told KXAS.

The Rancho Brazos and DeCordova Ranch neighborhoods in Granbury remained off limits after 97 of the 110 area homes were damages or destroyed.

“Some were found in houses. Some were found around houses,” Hood County Sheriff Roger Deeds said of the people killed in the storm. “There was a report that two of these people that they found were not even near their homes, so we’re going to search the area out there.”

The dark funnels of as many as 16 tornadoes touched down in northern Texas on Wednesday evening, according to a preliminary report by the National Weather Service.

Slideshow: Tornadoes hit Texas

Ralph Lauer / EPA

A series of tornadoes ripped across northern Texas, killing six and injuring dozens more.

Launch slideshow

The less powerful EF-3 tornado struck the nearby town of Cleburne, sweeping away parts of several homes, including one belonging to the family of Geraldine Williams.

“It’s devastating. It’s been ravaged,” Williams said as she sifted debris. The roof of the house was torn clean off, and mattresses were sucked up through the ceiling and tossed down in the backyard.

“It’s just weird, it’s so indiscriminate,” Williams told KXAS. “Look, that picture is hanging. Everything in the china cabinet was intact, but then look at my dad’s study, it just went ‘poof.’”

All of the deceased were from the Rancho Brazos neighborhood, authorities have said, where the non-profit group Habitat for Humanity had constructed 61 homes.

The dead were identified on Thursday as Jose Tovas Alvarez, 34; Robert Whitehead, 60; Tommy Martin, 61; Marjari Davis, 82; Leo Stefanski, 83; and Glenda White, whose age was unknown. 

Related:

• Search for Texas tornado survivors: Some victims 'not even near their homes'
• 6 dead, 7 missing as tornadoes rip through Texas
• Texas tornadoes devastate neighborhood built by residents, Habitat for Humanity

A tornado tore through the New Orleans area Wednesday, damaging homes and ripping trees out of the ground, as intense storms lashed the area with rain.

The National Weather Service (NWS) said the twister was one of two that caused damage in Kenner, Louisiana, near New Orleans International Airport.

No injuries were reported, according to the Times Picayune’s website NOLA.com, but about 5,000 Entergy Louisiana customers lost electrical service.

The first tornado's path stretched two miles and 75 yards wide and packed winds of 75 mph. The second's path was a half a mile long and 50 yards wide and recorded winds of 90 mph.

Residents posted pictures on social media of torn roofs, fallen trees and flash floods caused by torrential rains, weather.com reported.

Witness Adine Humphrey told NOLA.com: "The wind picked up. The rain picked up. You kind of heard that noise like a train a little bit. I looked next door. I seen the debris going in circles. I ripped my mother inside."

The NWS said the airport tower lost power during the storms, which struck during the middle of the day on Wednesday.

This story was originally published on Thu Apr 25, 2013 4:21 AM EDT