This item provides us a bird’seye view of the effects of what must be the greatest tornado event everrecorded. Tornado survival is always amatter of dumb luck. Getting close ifyou have a choice in the matter is never a good idea. They are always erratic and appear to have amind of their own.
A couple of weeks ago I heard anitem about the rare multi cell situation. Then we had just that erupt as if they were common.
Some time or the other we willaccept the reality of the risk and simply mandate every structure to include aproper cellar based storm shelter. Noproblem if simply included in the original design when it is naturally cheap. Concrete walls and a roof slab is prettysecure and it provides a cool storage closet.
Folks usually have time to runfor the cellar.
A Story from the Tornado Zone
Editor's Note:On Wednesday, April 27th, Science@NASA writer DaunaCoulter found herself near ground zero as a super-outbreak of tornadoes rippedthrough North Alabama . This is the story aboutthe science of the event she wrote and submitted from within the disaster zone.
April 27, 2011: Tornado sirens wailed all day long. They'd soundoff and then wind down for a little while, only to start up again a few minuteslater as forecasters spotted yet another hook echo on their radars andadrenaline-revved storm spotters confirmed the twisters that dropped fromseething skies one after another.
We lined our bathroom closet with blankets and pillows for my grandson.My husband kept going outside to look at the sky. If an atmosphere can becomesentient, the one out there was a malevolent, living thing. This was not yourusual storm. Even our Golden Retriever was pacing the floor.
In the late afternoon, we lost power. We scrambled to find our radio,batteries, flashlights, candles, and matches, as tornados continued to trainacross the area. The wind finally died down around 10 pm.
April 28, 2011: The power was still out when I woke up the morningafter the storm. I made coffee on our camp stove in the back yard and sat in alawn chair to listen to the radio. The news was worse than I'd expected. As thesun rose to begin an apologetically brilliant, clear day, I said a silentprayer for those who had lost their lives in the storms. They were, and stillare, on my mind and in my heart. (More than a week later, all the missing haveyet to be accounted for.)
I couldn't check on family or friends by cell phone until that evening,and even then phone service was spotty, as it would be for two more days. Thepeople I finally reached said they'd been trying to call me. Science@NASAeditor Tony Phillips was among them. When we finally talked, he made sure I wasokay and then said something that blew my mind: "I want you to write astory about this."
With no lights, no computer, spotty cell phone coverage?
"Okay," I answered, and then began figuring out how to do it.
April 29, 2011: The next morning I located a friend who lived nearthe Tennessee
What had caused a storm of this magnitude?
I emailed prospective interviewees at NASA and the National WeatherService, hoping they'd have internet service – and some answers. I urged mycontacts to call me as I had no computer access anywhere in Huntsville
By mid-afternoon, no one had called back, so it was time to try anothertack.
I drove to the National Space Science and Technology Center , a leading-edge severe weatherresearch center housing investigators from NASA and the University of Alabama as well as the NationalWeather Service's Forecast Office in Huntsville
I was glad to see a few cars in the parking lot and hear the hum of agenerator. Using my badge to enter the building, I made my way throughsemi-dark hallways to the Weather Service Office. There I found Larry Burgettof their Public Service Unit along with forecaster Jennifer Lee. Both of themwere part of a large team that had worked from 3:30 a.m. to 10 p.m. centraltime, nonstop, the day of the storm to track the event and alert the public.
"It was a day unlike any other," said Burgett. "We'venever issued so many warnings in rapid succession. And we've never had so manydamage reports in one day."
The field survey team2 examining the damage in north Alabama reportedone twister as an EF-5, a ranking reserved for the most violent and destructivetornadoes. It had peak winds of 210 mph, was 1.25 miles wide in spots, andstayed on the ground for 132 miles.
"Not only was there a tremendous outbreak of tornadoes – but manyof them ripped along the ground for a long time," said Lee. "It'svery unusual for that many funnels to stay down that long."
Burgett described some unbelievable sights: "Some homes were hitnot once but twice – by one tornado on the heels of another. That's unheard of.Maybe in a rare case you'll hear of a home being hit twice over several years,but not in the same day. And everywhere a tornado touched down – there wasmajor damage."
I drove home, digesting and mourning all I'd learned that day, yet noone had explained to me how this century-class catastrophe had happened. Howdid this storm brew enough energy to transform itself into such a monstroustornado-machine?
Later, NASA meteorologist Walt Petersen3 and UA-Huntsvillemeteorologist Tim Coleman called me with some facts.
"A deep cold batch of air in the central US seeped toward thesoutheast behind a cold front that trailed a ground-level low pressuresystem," explained Petersen. "Moist air from the Gulf of Mexico streamed in toward the lower-pressure area like waterheading for an open drain. Above that moist air, we had very strong winds withlots of wind shear.
That means that the wind turned and sped up with height, causing theupdrafts in the storm to corkscrew as they ascended into the turning wind.Collectively, those ingredients turned deadly, causing storms to form andintensify, and at the same time rotate because of the wind shear."
Coleman added: "This kind of set up in the atmosphere is extremelyrare. We have a number in meteorology called the EHI (Energy Helicity Index)4 thatindicates the likelihood of tornadoes developing. With an EHI over 2 you canexpect some tornadoes.
Over 5 and you can expect some significant tornadoes. The EHI predictedby computer models the day before this event was 10, and that prediction wascorrect."
Coleman admits that he was frightened by what he'd seen developing. Andas part of a storm survey team sorting through the rubble the day after themega-storm, he found that his fears had been realized.
"Brick homes were blown apart. Even above-ground walls of theirbasements were gone, and there were mountains of debris – including concreteblocks and large pieces of lumber – on basement floors. Some of these tornadoeswere almost unsurviveable. Only in a well-built storm shelter would you make itthrough."
April 30, 2011: As time allowed over the next few days, I workedon this story outside under a shade tree in daytime and inside by candlelightat night. Though I stayed busy the rest of the time heating water to washdishes, waiting in long lines to buy ice and gas from the few stores withgenerators, and checking on my elderly parents, life had, in a sense, slowedand quieted. No televisions blaring, no air conditioners humming, no weedeaters buzzing. (The extra gas was needed in cars.) Even the dogs wereunusually silent. I've never slept better.
In any other circumstances, you'd think we were all enjoying anextended holiday. People were out all over town walking to the store, biking,visiting with one another. And they kept their good spirits and sense of humorthrough it all. One neighbor posted thissign.
In the evenings, our neighbors brought the contents of their defunctrefrigerators and freezers over to share, and we cooked out on grills and thecamp stove. Communities all over town had similar gatherings. My 86 year oldfather, who cares and cooks for my semi-invalid mother, reported each day onwhat their neighbors had brought them for supper. "We've been eatingbetter than we ever did with my cooking!" he said.
At night the city was so dark, it was like living in a differentcentury. I rode my bike under the stars. Replacing the gaudy glare ofincandescent lights, a soft glow of candlelight issued from the windows ofneighbors' homes. Some families gathered around backyard fires. And with noteven a moon in view, I saw stars I'd never seen before. There above me was thewhole Milky Way!
May 2, 2011: It's been a bittersweet week.
I was sitting in the back yard last night as a wave of cheering andyelling started in the distance and seemed to roll toward me. It grew louderand louder, closer and closer, building to this crescendo: my son leaning outthe back door and shouting, "We have power!"
People were cheering as the lights came on swiftly, street by street,across the neighborhood.
"Let there be light!" (That was me, joining the sound wave.)
I'll remember these experiences for a long, long time: Slow, haltingdrives through the city with no street lights working, waiting in long linesfor a ration of ice or gas or to buy a few hotdogs for the grill, curfews,taking ice cold showers, fumbling around in the darkness for my toothbrush,stubbing my toes in dim rooms … and thinking of those who were not asfortunate.
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