This item provides us a bird’s
eye view of the effects of what must be the greatest tornado event ever
recorded. Tornado survival is always a
matter of dumb luck. Getting close if
you have a choice in the matter is never a good idea. They are always erratic and appear to have a
mind of their own.
A couple of weeks ago I heard an
item about the rare multi cell situation.
Then we had just that erupt as if they were common.
Some time or the other we will
accept the reality of the risk and simply mandate every structure to include a
proper cellar based storm shelter. No
problem if simply included in the original design when it is naturally cheap. Concrete walls and a roof slab is pretty
secure and it provides a cool storage closet.
Folks usually have time to run
for the cellar.
A Story from the Tornado Zone
Editor's Note:On Wednesday, April 27th, Science@NASA writer Dauna
Coulter found herself near ground zero as a super-outbreak of tornadoes ripped
through North Alabama . This is the story about
the science of the event she wrote and submitted from within the disaster zone.
April 27, 2011: Tornado sirens wailed all day long. They'd sound
off and then wind down for a little while, only to start up again a few minutes
later as forecasters spotted yet another hook echo on their radars and
adrenaline-revved storm spotters confirmed the twisters that dropped from
seething 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 become
sentient, the one out there was a malevolent, living thing. This was not your
usual 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 train
across the area. The wind finally died down around 10 pm.
April 28, 2011: The power was still out when I woke up the morning
after the storm. I made coffee on our camp stove in the back yard and sat in a
lawn chair to listen to the radio. The news was worse than I'd expected. As the
sun rose to begin an apologetically brilliant, clear day, I said a silent
prayer for those who had lost their lives in the storms. They were, and still
are, on my mind and in my heart. (More than a week later, all the missing have
yet 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. The
people I finally reached said they'd been trying to call me. Science@NASA
editor Tony Phillips was among them. When we finally talked, he made sure I was
okay and then said something that blew my mind: "I want you to write a
story 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 near
the Tennessee
What had caused a storm of this magnitude?
I emailed prospective interviewees at NASA and the National Weather
Service, hoping they'd have internet service – and some answers. I urged my
contacts 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 another
tack.
I drove to the National Space Science and Technology
Center , a leading-edge severe weather
research center housing investigators from NASA and the University
of Alabama as well as the National
Weather Service's Forecast Office in Huntsville
I was glad to see a few cars in the parking lot and hear the hum of a
generator. Using my badge to enter the building, I made my way through
semi-dark hallways to the Weather Service Office. There I found Larry Burgett
of their Public Service Unit along with forecaster Jennifer Lee. Both of them
were part of a large team that had worked from 3:30 a.m. to 10 p.m. central
time, nonstop, the day of the storm to track the event and alert the public.
"It was a day unlike any other," said Burgett. "We've
never issued so many warnings in rapid succession. And we've never had so many
damage reports in one day."
The field survey team2 examining the damage in north Alabama reported
one twister as an EF-5, a ranking reserved for the most violent and destructive
tornadoes. It had peak winds of 210 mph, was 1.25 miles wide in spots, and
stayed on the ground for 132 miles.
"Not only was there a tremendous outbreak of tornadoes – but many
of them ripped along the ground for a long time," said Lee. "It's
very unusual for that many funnels to stay down that long."
Burgett described some unbelievable sights: "Some homes were hit
not 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 was
major damage."
I drove home, digesting and mourning all I'd learned that day, yet no
one had explained to me how this century-class catastrophe had happened. How
did this storm brew enough energy to transform itself into such a monstrous
tornado-machine?
Later, NASA meteorologist Walt Petersen3 and UA-Huntsville
meteorologist Tim Coleman called me with some facts.
"A deep cold batch of air in the central US seeped toward the
southeast behind a cold front that trailed a ground-level low pressure
system," explained Petersen. "Moist air from the Gulf
of Mexico streamed in toward the lower-pressure area like water
heading for an open drain. Above that moist air, we had very strong winds with
lots of wind shear.
That means that the wind turned and sped up with height, causing the
updrafts in the storm to corkscrew as they ascended into the turning wind.
Collectively, those ingredients turned deadly, causing storms to form and
intensify, and at the same time rotate because of the wind shear."
Coleman added: "This kind of set up in the atmosphere is extremely
rare. We have a number in meteorology called the EHI (Energy Helicity Index)4 that
indicates the likelihood of tornadoes developing. With an EHI over 2 you can
expect some tornadoes.
Over 5 and you can expect some significant tornadoes. The EHI predicted
by computer models the day before this event was 10, and that prediction was
correct."
Coleman admits that he was frightened by what he'd seen developing. And
as part of a storm survey team sorting through the rubble the day after the
mega-storm, he found that his fears had been realized.
"Brick homes were blown apart. Even above-ground walls of their
basements were gone, and there were mountains of debris – including concrete
blocks and large pieces of lumber – on basement floors. Some of these tornadoes
were almost unsurviveable. Only in a well-built storm shelter would you make it
through."
April 30, 2011: As time allowed over the next few days, I worked
on this story outside under a shade tree in daytime and inside by candlelight
at night. Though I stayed busy the rest of the time heating water to wash
dishes, waiting in long lines to buy ice and gas from the few stores with
generators, and checking on my elderly parents, life had, in a sense, slowed
and quieted. No televisions blaring, no air conditioners humming, no weed
eaters buzzing. (The extra gas was needed in cars.) Even the dogs were
unusually silent. I've never slept better.
In any other circumstances, you'd think we were all enjoying an
extended 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 humor
through it all. One neighbor posted this
sign.
In the evenings, our neighbors brought the contents of their defunct
refrigerators and freezers over to share, and we cooked out on grills and the
camp stove. Communities all over town had similar gatherings. My 86 year old
father, who cares and cooks for my semi-invalid mother, reported each day on
what their neighbors had brought them for supper. "We've been eating
better than we ever did with my cooking!" he said.
At night the city was so dark, it was like living in a different
century. I rode my bike under the stars. Replacing the gaudy glare of
incandescent lights, a soft glow of candlelight issued from the windows of
neighbors' homes. Some families gathered around backyard fires. And with not
even a moon in view, I saw stars I'd never seen before. There above me was the
whole 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 and
yelling started in the distance and seemed to roll toward me. It grew louder
and louder, closer and closer, building to this crescendo: my son leaning out
the 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, halting
drives through the city with no street lights working, waiting in long lines
for 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 as
fortunate.
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