Recipe for a disaster: How this week's tornadoes formed
In Alabama, the hardest-hit state, the storms destroyed hundreds of businesses and homes, such as this one in Tuscaloosa.
April 29th, 2011
01:54 PM ET

Recipe for a disaster: How this week's tornadoes formed

A wave of storms swept through the South this week, laden with tornadoes that killed at least 300 people and left a multistate trail of destruction.

As authorities continue to assess the damage, recover bodies and restore power to thousands of homes and businesses in the storm zone, weather experts have many questions about the confluence of factors that formed such a violent weather system.

Did a perfect storm of sociological, meteorological and geographical events combine to create the second-deadliest tornado outbreak in the nation's history since 1950? The University Corporation for Atmospheric Research's Bob Henson, who recently wrote about the recipe for the storms, said it seems that way, but perfection is relative.

"You never know what’s perfect, because there may be another storm that’s even more perfect. Many say the 1974 super outbreak was the ultimate event," he said.

In 1974, a super outbreak of tornadoes churned through 13 states, killing hundreds of people.

One thing is certain: Way before Wednesday's storms came, forecasters saw the ingredients for trouble in the skies.

Weather forecasters had "very, very strong signals actually about five days out indicating a significant weather outbreak," Greg Carbin, warning coordination meteorologist at NOAA's Storm Prediction Center, told CNN on Friday.

But "saying a significant weather outbreak is coming is quite different from saying a massive tornado will move through Tuscaloosa at 5 p.m.," Carbin said. "So knowing the big picture is pretty good, but you don’t know the specifics; you only know really after the thunderstorm begins to form."

Around midday Wednesday in Mississippi, funnel cloud reports began.

“Tornadoes typically form from what are called super-celled storms,” Greg McFarquhar, a professor in the Atmospheric Sciences Department at the University of Illinois, told CNN on Friday. “You need a number of different ingredients. One is warm, humid air toward the surface. You need some sort of trigger that will start that air rising, that is associated with a cold front, and then a third ingredient is instability in the atmosphere,” he said.

“When a parcel of air starts to rise, if it’s warmer than the surrounding air, it’s going to be less dense than the surrounding air, and it will continue to rise,”  McFarquhar said.

Throughout the day Wednesday, the National Weather Service issued tornado watches - a "particularly dangerous situation" - for parts of Mississippi, Alabama, Tennessee, South Carolina and Georgia.

Other agencies were issuing advisories as well. NOAA’s Storm Prediction Center in Norman, Oklahoma, issued its highest threat warning - “high risk” - for parts of the South. Shortly after, the prediction center issued red-colored headlines on its advisories, noting the likelihood of “destructive tornadoes … large hail up to 4 inches in diameter … and dangerous lightning.”

Another crucial ingredient was wind shear: volatility in wind speed and direction.

"Storms happen all the time," Carbin said, "but for those storms to last, you need wind shear.  If not, it will actually self-destruct. Wind shear will allow the storm to form a very efficient chimney, so to speak," he said.

On top of it all was a fast-moving storm system that raked parts of six states.

"It first showed up in Mississippi," Carbin said, "and at the same time, it wasn’t just one storm, it was five, 10, 15 erupting one after another in a 30-minute span. We know that. What we don't know is how to provide a specific pinpoint forecast of a violent tornado. That's still out of reach."

Armed with data from the National Oceanic and Atmospheric Administration and the National Weather Service, meteorologists in the affected regions went live with coverage of the storms’ path. But there was a major problem in getting the word out.

High winds associated with the storm had already caused power outages in several areas of the tornado zone as tree limbs snapped and power lines fell. Henson said he heard anecdotally that some NOAA weather radio transmitters were down as well, adding to the confusion.

Among the series of storms was at least one, in Smithville, Mississippi, that was an EF5. The National Weather Service in Memphis, Tennessee, said Friday the twister was Mississippi's first EF5 in more than 40 years.

An EF twister generates winds of more than 200 mph, according to the National Oceanic and Atmospheric Administration.

Soon afterward, witnesses reported tornado touchdowns in parts of Alabama.

In Alabama, where most of the damage was done, media and residents are calling another twister, captured on video, simply a "monster."

But how could so many people perish in an event that was forecast?

"Sometimes, we assume that getting the warnings issued is the only task that needs to be done, " Henson said. "But we're seeing that even when the warnings are out, we can still have many people killed."

He said the death toll may speak more to how people live today. "You can have perfect warnings, but if people don’t act on them … and when you have an event this big, you’re going to have some casualties. The open question is: Did there have to be 300?”

"I am concerned that there are a lot of places where safe shelter is just not a priority," Henson said.

Carbin said storms need to be studied more, particularly when many factors are involved.

"Once a storm becomes part of an environment, does it enhance wind conditions or deteriorate them?" he said. "We still don’t understand all of those interactions yet."

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Filed under: Alabama • U.S. • Weather
soundoff (85 Responses)
  1. Mike

    What are you doing about your tax dollars going overseas ? IRAQ, LYBIA, SOON SYRIA AND WHEREVER BUSH IS HIDING BIN LADEN.

    April 30, 2011 at 3:06 am | Report abuse |
    • Tornado Alleycat

      Time for beddy bye sonny boy. Kiss your dolly goodnight... and TRY to wake up on the right side of the bed tomorrow.

      April 30, 2011 at 9:09 am | Report abuse |
  2. Bdo

    Can't they just make a tornado app for smartphones? If people are reporting a tornado in your area and we know our phones track our whereabouts why can't we have somewhat reliable tornado warnings ground level.

    April 30, 2011 at 3:13 am | Report abuse |
  3. Sabrina

    Jacob, feel no need to downplay your comments. I support them whole-heartedly and second them. To bring politics into a discussion on human life, is about as low brow as bringing in religion, as "god hates the south" or some akin b.s. Jacob's meandering thoughts are filled with logical inconsistencies and quit boring actually. I stopped reading when his train de-railed by not considering the fact that visitors from other states are there, and legally allowed to visit and conduct trade in these states. Are they to be afforded no protection in jacob's mockery of intelligent thought? Interstate commerce=FEDERAL. Let me end mine by saying, Jacob, you ramble like an idiot dude, so PLEASE shut the f*** up.

    April 30, 2011 at 3:13 am | Report abuse |
  4. Archie Bunker

    They control the weather along with the HAARP project.

    http://www.naiwmc.org/

    I hope no one here lives in alabama or close to this nuclear station.

    http://pesn.com/2011/04/29/9501819_..._Spur_Nuclear_Emergency_in_Alabama/

    April 30, 2011 at 3:18 am | Report abuse |
  5. Sabrina

    Forgive me Jacob! It's 3 am. Re-posted ! Jacob, feel no need to downplay your comments. I support them whole-heartedly and second them. To bring politics into a discussion on human life, is about as low brow as bringing in religion, as "god hates the south" or some akin b.s. DanteX's meandering thoughts are filled with logical inconsistencies and quit boring actually. I stopped reading when his train de-railed by not considering the fact that visitors from other states are there, and legally allowed to visit and conduct trade in these states. Are they to be afforded no protection in DantX's mockery of intelligent thought? Interstate commerce=FEDERAL. Let me end mine by saying, DantX, you ramble like an idiot dude, so PLEASE shut the f*** up.

    April 30, 2011 at 3:20 am | Report abuse |
  6. Candidradio.com

    Bdo,
    Buy a AC and battery backed up NOAA radio. Midland makes them. Check out NOAA.gov. As a weather spotter, this radio is like a smoke detector for fires.

    April 30, 2011 at 3:33 am | Report abuse |
  7. stryker

    Mass underground shelters are only good if your very near the shelter. A lot of people would be killed just trying to make it to the shelter. You have very little time to take shelter after the sirens go off were I'm from in kansas we usually have about 10 to 12 min and that's not enough time to get to a community shelter. Personal storm shelters are the only way to go.

    April 30, 2011 at 4:17 am | Report abuse |
  8. rhysinn

    Agreed. Living in Oklahoma, you have 10 to 15 minutes when the sirens sound off. Telling people to seek out the nearest community shelter would get a lot of folks killed in their driveways.

    April 30, 2011 at 5:57 am | Report abuse |
  9. Suresh Puthileth

    Hi just out of curiosity was there research done on how to break this, since we almost know it is due to certain factors. Is it possible to negate that like bring down the pressure around it thru some technology means? It might sound stupid, but something of that nature was already done can you provide some info around it.

    April 30, 2011 at 6:59 am | Report abuse |
  10. Sandy

    There are people on some of the other message boards that say that God helped them, spared them or whatever and it's greeted with more comments such as "if God exists then why does he let the children die? Or they don't believe because they can't see him?" God DOES exist but you have to have that faith. Do you love your children? family? Why should people believe that just because you say you do? Your significant other has to have faith that you love him/her. I think God simply does not intervene at times just like when Jesus was on the cross God did not intervene but let his son die as a sacrifice for the rest of the world. You may not believe in God right now but trust me your day will come and you WILL believe only it's gonna be too late for you. You're going to beg and plead for him to believe you and he will turn away and say "I never knew you". Too bad to be you. I'm from the South and had plenty of scares myself on Wednesday and people should thank God that they are still here cause it's too late for alot of those people. I can assure you if there were unbelievers amongst the dead they believe now. I think sometimes God simply lets bad things happen maybe just to get other peoples attention. I myself lost my first born at the age of 2 months 30 years ago. I was mad at God and everyone else. I didn't understand why God would take my child that was sooo wanted and loved and then I would hear on TV of people who abandoned babies in dumpsters, bathrooms, etc. I could comprehend why he would take mine because we wanted our baby at ANY cost. In retrospect I think God done what was best for us as the time and he spared us alot of medical bills, doctors, surgeries, etc because it would have been a never ending thing for our son, he would never have been able to have the kind of life we wanted for him but we didn't understand that for a long time. However he did go on to bless us with 2 beautiful, healthy girls that are now grown. He always knows whats best. BELIEVE, even though he knows you don't love him, he loves you.

    April 30, 2011 at 7:46 am | Report abuse |
    • fishnn machine

      I hope you feel great bringing religon in to this tragedy...no one here has blame go for what happend ,so I don't know what on earth are you talking about...we love god and belive in god but rite now we are talking about the tornado victims and what might help for next time ....quit shoveing your religon down our throats,church is on Sunday,tomorrow.......you probably one of dose church people that talks about every one else in church....hope a tornado goes up your a hole 🙁

      April 30, 2011 at 10:50 am | Report abuse |
    • Jay

      Yea..have "faith".. "And god loves you even though he knows you don't love him".. I guess that's he loves you so much you got punched in the face by a tornado... Get that religious BS outta here and get a grip on REALITY!!!

      April 30, 2011 at 5:48 pm | Report abuse |
  11. Mr. Ashley Perez

    My heart goes out to the family, friends of the above-mentioned states. No words can express how saddened I'm am over the loss due to natures wrath. However, I am also saddened at the possibility of these weather patterns being man made. HARP! can it be, such a perfect storm. Weather conditions where likened to that of a perfect recipe. High & low pressure perfect 4 inch size hail. The path of the storms as if directed, guided. The time from touch down to dissipation well over 25-30 min. An event that big and the total amount of destruction record breaking. I started to ask my self, 1974 & 1950 greatest storms on record for this area. Some 30 years later another. This is strange, the pattern of the storms its strength. People, once you are healed ask your congress about HARP & its financers. Was this a freak of nature or another test that resulted in so much death and distruction. Test, successful... God be with you all.

    April 30, 2011 at 8:13 am | Report abuse |
  12. Mr. Ashley Perez

    HARP ASK QUESTIONS

    April 30, 2011 at 8:17 am | Report abuse |
  13. Mr. Ashley Perez

    HARP ASK QUESTIONS!

    April 30, 2011 at 8:18 am | Report abuse |
  14. Jill

    Dantex,
    U are a heartless twit. The first thing u need to remember is that many of the people who move to the south do so 'cause it's simply cheaper to live there than anywhere else. They don't have the luxery of building their own homes or even chosing to live in one that has a basement. They have to take what they can get. So for u to say such thoughtless things shows u haven't a clue what it's like to live in the South.

    April 30, 2011 at 8:28 am | Report abuse |
  15. Say what?

    You posted to the wrong article Chico. Take your medications before you hit the enter key.

    April 30, 2011 at 9:02 am | Report abuse |
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