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Crossposted to State of the Skies

Today is the one year anniversary of the worst tornado outbreak in recorded American history. On this day in 2011, 206 tornadoes touched down across 16 states to kill 322 people, leave tens of thousands homeless, and cause billions of dollars in damage. This was the single deadliest weather-related day in the United States since Hurricane Katrina came ashore 6 years earlier.

What was remarkable about this generational tornado outbreak was not only the sheer magnitude of the event, but the way in which we were able to get warnings and watch the worst tornadoes wreak havoc on live television. Many television stations in Alabama were able to capture the worst tornadoes on live television using tower cameras placed throughout the state. Meteorologist James Spann of ABC 33/40 was able to tell Tuscaloosa residents exactly where the tornado was because it was caught live on camera. YouTube user jbbbrown2 has almost all of ABC 33/40's tornado coverage on YouTube, if you want to watch the day unfold as it happened.

Many of us here at DailyKos watched it unfold as it happened. I skipped classes that day so I could watch the weather and keep up with what was going on. I liveblogged the outbreak for over 12 hours here on DailyKos, and I remember sitting there in shock of what I was watching on television. It's...surreal...watching a live tornado tear apart both people and their lives.

Back in December of last year, I wrote a recap of the year's major tornado outbreaks, including a lengthy section on this tornado outbreak. Over the fold I've reproduced the April 27th section of the diary, as well as my commentary below it. I've added some pictures, videos, and text that I feel help tell the story.

An extremely strong weather system moved across the southern United States between April 25 and April 28, with the worst weather occurring on Wednesday April 27. The tornado outbreak of April 27th broke numerous records:

  • It was the second deadliest single tornado outbreak in American history (322 people died)
  • It was the costliest tornado outbreak in American history (~$11 billion in damages)
  • It produced the most tornadoes ever recorded in one outbreak (353 tornadoes over 3 days)
  • The most tornadoes ever recorded in 24 hours (199 confirmed)
  • The second most EF5/F5 tornadoes ever recorded in 24 hours (4)

A warm, humid airmass at the surface, combined with strong lift ahead of a cold front and upper-level trough allowed massive thunderstorms to develop across much of the southeast. Add in very strong vertical wind shear, and the storms turned into supercells and began to spin like tops on steroids. The result was catastrophic. Weather models saw these ingredients coming together, and the SPC had predicted a massive tornado outbreak for Mississippi and Alabama a few days in advance of the system. By the morning of April 27th, they had issued a rare high risk area over the most unstable airmass -- stating that there was a 45% (almost unheard of) risk for significant tornadoes that day.


Severe weather risk for April 27 2011

The storms came in two rounds. The first round happened pre-dawn on April 27, and came in the form of a squall line with some embedded weak tornadoes. The squall line was extremely intense -- its winds knocked down trees, power lines, destroyed mobile homes, and completely demolished some radio and cell phone towers. This left tens of thousands of people in northern Alabama without power, without telephones, and without cable to start the day. The early morning line of storms also knocked out numerous weather radio towers across northern Alabama, rendering weather radios useless for the bigger outbreak later in the day. Many of the deaths from the tornadoes that would form later in the afternoon came from people not knowing about the tornadoes due to power outages, phone outages, and weather radio outages. The death toll may have been lower had the early morning squall line not formed and knocked out these vital lines of communication.

Starting around mid-afternoon, instability was sufficient enough to fire off the nasty supercell thunderstorms that would produce all the death and destruction. It would be impossible to cover the hundreds of tornadoes that formed, so I'll focus on the 6 most destructive and deadly ones.


All tornado warnings issued between 7AM (ET) April 27 and 7AM (ET) April 28, 2011.

Storm reports. Red = tornado, blue = wind, green = hail.




Cullman EF4 Tornado

Early in the afternoon, a supercell formed near the northern Alabama town of Cullman. Meteorologist James Spann, who works for ABC 33/40 out of Birmingham, covered the tornado live on tower cam as it formed in downtown Cullman and tracked through the city and into Arab. The EF4 tornado produced extensive damage to businesses, homes, and historic buildings in the downtown area. The tornado killed 6 people.




Tuscaloosa/Birmingham EF4 Tornado

Probably the most (in)famous tornado of the outbreak was the long track, monster tornado that tracked northeast from the southwestern suburbs of Tuscaloosa AL to the northeastern suburbs of Birmingham AL. This borderline-EF5 tornado caused extensive damage across its 88 mile-long path, and the tornado was 1.5 miles wide at times. This tornado killed 63 people and injured more than 1500. What made this tornado unique is that it was caught by literally hundreds of video cameras, and it was broadcast on live TV for almost its entire lifespan.

Here's ABC 33/40 coverage of the tornado as it tore through Tuscaloosa:

A resident of Tuscaloosa took a video of the tornado as it approached his apartment complex. He should not have done this, and if you're ever in the unfortunate position to encounter a tornado this close, do not do this.

The Weather Channel was stationed on a lookout over the city of Birmingham, and caught a terrifying view of the tornado as it tore through the suburb of Pleasant Grove. The tornado is so large and intense at this point that it's nearly impossible to tell with the naked eye where the tornado stops and the storm's mesocyclone (which descended to ground level) begins.

The radar images that came out of the storm are just as terrifying as the tornado itself.  The first image below is the radar as the tornado was tearing through the heavily populated areas of Tuscaloosa. It's a textbook supercell, with the debris ball (the dark red/purple dot on the southern side of the hook in the storm) visible.

This image is a 3D analysis of the thunderstorm as it skirted north of Birmingham. The image looks at the storm from the bottom of the radar scan up through the top of the thunderstorm, with only the darkest reflectivities showing. The dark red/purple column in the middle of the image is actually the tornado full of debris, throwing it tens of thousands of feet in the air. For a few days after the outbreak, they were finding small stuff like letters, clothes, and pictures over 150 miles away from where they originated.


Smithville, MS EF5 Tornado

Smithville MS was struck by the first of four EF5 tornadoes to form that day. The tornado killed 23 people, scrubbed dozens of homes and other buildings down to their foundations, and even scoured drainage pipes out of the ground. A simple picture and caption from the NWS website is able to describe the unbelievable power of this tornado:


The remains of a Ford Explorer in Smithville MS. The tornado hurled the SUV about ½ mile, into the town's water tower (the tower is in the picture background) and continued on another 1/4 mile until impact. (Photo: Mississippi Emergency Management Agency)



Alabama/Tennessee (Hackleburg) EF5 Tornado

The second of the four EF5 tornadoes tore through parts of northwestern Alabama and southern Tennessee. The tornado tracked 133 miles that afternoon, with a maximum width of 1.25. The storm killed 72 people, and was the single deadliest tornado in Alabama history.

Here is an aerial video of the damage in Hackleburg from ABC 33/40. Caution: Some images are graphic.




Rainsville AL EF5 Tornado

The third of four EF5 tornadoes occurred in Rainsville AL, which is on the northeastern side of the state. The tornado was 1/2 mile wide at its largest, and killed 23 people. The storm that produced this tornado would go on to produce an EF4 tornado in Ringgold GA about an hour later.

By chance, I wound up staying the night just a few hundred feet away from the path of the EF-5 that hit Rainsville, AL that day. Over the summer when my mom and uncle were bringing me back to Mobile for school, we happened to stay at a hotel that was just a few hundred feet to the southeast of where the EF-5 tore through 3 months earlier. It was pitch black when we got there and most of the roads still didn't have streetlights yet, so we missed the turn for the hotel and wound up going down a residential street. We turned around in what used to be a house's driveway (there was nothing left but a concrete slab), and when the headlights shined on the field behind us, I gasped out loud. Hundreds of debarked trees and large pieces of destroyed homes littered the field. It was like a scene out of a movie, and it was 3 months after the tornado. By light the next morning, you could see where they were rebuilding the Rainsville Community Center, and the foundations of where the destroyed buildings used to stand. There was insulation in the grass and trees, and next to the hotel there was a huge 15 or 20 foot metal panel wrapped 4 times around a tall tree. As we drove out, there was still some debris strewn about on a patch of gravel next to the hotel:

I felt awful for the people who not only lost loved ones, but lost their homes. I can't imagine what it's like having to spend months cleaning up what it took you a lifetime to put together.

Here's a storm survey picture from the NWS, showing what's left of a school bus, next to the Rainsville Community Center, which was also destroyed. The hotel we stayed at is actually the building visible on the far left part of the image.




Ringgold GA EF4 Tornado

About an hour after the Rainsville/DeKalb County AL tornado struck, the supercell lifted off to the northeast into the northwestern part of Georgia. The storm gained its rotation back and dropped a tornado near the town of Ringgold. The tornado strengthened into an EF4 by the time it reached the town, destroying dozens of homes and businesses, and causing damage so bad that all roads going into or out of Ringgold were closed by police. The tornado tracked across 52 miles of real estate, and killed 20 people, before finally lifting and moving off to the northeast. The storm would continue to produce smaller tornadoes throughout the night.



Why were there so many tornadoes in 2011?

We got caught in an extremely active weather pattern. The jet stream was strong enough and sagged far enough south to create strong weather system after strong weather system. These systems were able to tap into the south's warm, humid air and create big thunderstorms. These storms benefited from strong wind shear, and it led to constant tornado outbreaks. The amount of thunderstorms that developed increased the chances of some of these storms tapping into the perfect ingredients for strong tornadoes, and as we saw, they took that opportunity one too many times.

Also, it helps to look at previous years in explaining this year's pattern. Here's a totally awesome Excel chart I made, using tornado 2011-2008 tornado statistics from the SPC:

The majority of this year's tornadoes came from the increased activity in April. With other years, there is a peak in tornado activity in the spring, with a very gradual drop-off throughout the rest of the year. However, in 2011, there was a massive spike in tornado activity in April and May, with a large drop in activity through the rest of the year. Again, this can be attributed to the active weather pattern we were in this year.

Did climate change contribute to the amount/intensity of these tornadoes?

Short answer: we don't know yet. One bad weather year isn't enough data to give a definitive yes-or-no answer. Climate change is definitely taking place, but even the NRDC concedes in its 2011 extreme weather wrapup that we can't be sure yet:

There were also another 7 extreme tornado events in 2011 with greater than $1 billion in damages each not shown on the map. We don't know yet whether climate change will worsen tornadoes – additional studies are needed.
Some years are extremely bad, some years are dead quiet. If this year's tornadic activity persists over the next decade, something is definitely up. My guess, though, is that the activity this year was a once-in-a-generation type event, like 1925 or 1974. Hopefully that's not proven wrong.

Why were the tornadoes in 2011 so intense?

One thing to keep in mind is that tornado intensity is measured with the Enhanced Fujita Scale, which measures tornado intensity based off of damages caused by the tornado. Trained meteorologists estimate the wind speeds based off of the severity of the damage caused. Roof tiles missing indicate an EF0 tornado, while a well-built home completely wiped off its foundation signals an EF5 tornado.

The tricky thing about tornado intensity is that the strongest part of a tornado has to hit a populated area for us to know truly how strong the tornado was. A tornado of EF5 intensity (200+ MPH winds) could go through an open field and not touch a structure, and it's automatically classified an EF0. The rating/intensity is based off damage. As people in our country continue to build and expand, more tornadoes are hitting populated areas, causing major damage and more opportunities to rate tornadoes somewhat accurately.

Aside from the technicalities of tornado measurement, the storms this year were pretty intense. I attribute this to the uptick in activity this year. More storms forming allows for greater chances of storms tapping into the perfect ingredients needed to spawn major tornadoes.

Every year on average, 80 people die in tornadoes. Why was the 2011 death toll nearly seven times the yearly average?

It can be attributed to 6 things:

1) While we have pretty good lead times on tornadoes (20+ minutes most of the time), most of these storms were moving at 50 or 60 MPH. That doesn't leave much time for hesitation when a warning is issued. Also, you have to keep in mind that people are people. Some of those who died ignored the warnings. Some didn't take them seriously. Some took them seriously and went outside to look, only to be killed before they could reach shelter. And unfortunately, some people just didn't have time to make it to shelter after receiving a warning.

2) To be frank, many of the tornadoes that hit populated areas were simply not survivable unless one was underground. Look at damage pictures from Tuscaloosa, Birmingham, Joplin, Cullman, Rainsville, El Reno, Hackleburg, and many other cities that were hit by EF4 and EF5 tornadoes. Simply taking cover in an interior bathroom or closet wasn't adequate enough to survive such intense tornadoes.

3) In the instance of the Alabama tornado outbreak on April 27, a nasty line of storms that formed hours before the tornado outbreak knocked out power to tens of thousands, destroyed NOAA weather radio towers, and seriously damaged telephone/cell phone systems. This hampered efforts to get out crucial tornado warnings to the public in parts of Alabama that were leveled.

4) In the case of the Joplin tornado, the sirens went off numerous times warning of the storm, and residents were somewhat numb to the effect of the warnings. This "Crying Wolf" effect is also a major factor in other tornado deaths, as one becomes complacent after hearing tornado warnings that don't come to fruition.

5) The tornadoes hit populated areas. Tornadoes usually stay over relatively unpopulated areas of the midwest, but this year's tornadoes were farther south, allowing them to strike more populated areas. As I said above, as people continue to expand and build in areas that were previously open fields, the chance of a tornado to hit homes and businesses rises.

6) Urban legends prove to be killers sometimes. NOAA interviewed (though I can't find the links anymore) people from across the south after these outbreaks, and found that the typical urban legends are more prevalent than once thought. The classic widely-believed myth is that "tornadoes can't cross mountains, bodies of water, or cities." This has proven fatal, and this complacency was the cause of a few of this year's deaths.

Meteorologists are constantly working on ways to improve and update warning systems, but sometimes these efforts just aren't enough when faced with strong tornadoes hitting populated areas. This year was proof of that.

What can I do to protect myself if I'm in the path of an intense tornado?

  • Get underground. If you have a basement, get into the most underground part of the basement you can, keeping in mind what is in the house directly above you and where you are in relation to things like gas lines and water heaters. If you cannot get underground, get into the most interior room of your house. Many of the survivors of the tornadoes last year survived only because the most interior room of their house (usually a small bathroom on the first floor) is the only room that wasn't obliterated.
  • Put on jeans, sturdy shoes, jackets, gloves, scarves, and a motorcycle helmet. One of the things you hear about but don't really think about are the kinds of injuries and deaths that occur in a tornado. Most people die due to gruesome trauma to the head. Most injuries are from lacerations, broken bones from debris impacts, or debris outright impaling your body. You want to do as much as possible to protect your body from flying debris, and that includes putting on a helmet. You'll look silly, but it's better to look silly than dead.
  • Do not take shelter under a roadway overpass unless you're suicidal. Taking shelter under an overpass is probably the stupidest thing you can do aside from driving straight into the tornado. Tornadic winds are amplified under a bridge, and they can easily sweep you out into the open. Plus, parking your car under a bridge can lead to a traffic jam if others follow your dumb lead. If you're out driving and there's a tornado, try to drive away from it if you can easily tell the direction and you know the area well. If you can't drive away or if you can't tell which way it's going, find a sturdy building like a school, business, or home. They'll likely let you in.
  • Do not go outside looking for the tornado. It's tempting, but it's closer than you think, you might not have time to react and get back inside to safety. Trust the experts when they say there's a tornado warning, especially when they say a tornado has been spotted.
  • Check the weather often. Use the Storm Prediction Center and the National Weather Service to keep tabs of dangerous weather in your area.
  • Get a weather radio with S.A.M.E. technology. Every home needs a smoke detector and a S.A.M.E. enabled weather radio. S.A.M.E. (Specific Area Message Encoding) allows you to program local county codes into the receiver, and allows it to automatically sound a loud tone when a watch or warning is issued.

Of course, this isn't an exhaustive list. Both the SPC and FEMA have a larger list of tornado safety tips.

Originally posted to El Blogo de Weatherdudeo on Fri Apr 27, 2012 at 01:25 PM PDT.

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