Though Tornado Alley in the American Great Plains has a reputation for being a hotbed for tornadic activity, it’s more lethal cousin lies just next door. Dixie Alley, in the southeast US, has become the deadliest region for tornadoes in the world. But what is causing this increase in destruction and how can we stop it?
Tornadoes can and have occurred in every state in the US at least once within the last one-and-a-half centuries (the timeframe of recorded atmospheric data). They can appear often without warning, seemingly anywhere given the right conditions. Perhaps the most well-known region on Earth for tornadic activity is Tornado Alley in the United States. Stretching across much of the Great plains from Texas into southern Minnesota, the area has quite literally made a name for itself for the concentration of tornadoes experienced on an annual basis. Few other places on Earth experience the right concoction of intersecting continental and marine jet streams that make these tornadoes so common.
Due to its grid-like road infrastructure and lack of visually obstructive trees, Tornado Alley has obviously attracted meteorological researchers from across the globe. Thus, a huge portion of media attention and public perception regarding tornadoes has been derived from this region.
However, what makes tornadoes so frightening is not their frequency but their ability to destroy. To that note, recent media attention has been shifting to an entirely different geographic area in the US. “Dixie Alley” is the name coined to describe the area in the Southeast US stretching from western Louisiana into North Carolina. Not only have the frequency of tornadoes in Dixie Alley began to rival Tornado Alley, but the amount of destruction is staggering. Over the past three decades, tornadoes in this region have been responsible for roughly thirty deaths per year, far outpacing Tornado Alley mortality rates. Cataclysmic events such as the 2008 Super Tuesday tornado outbreak (87 tornadoes, 57 killed) and the tornadic outbreaks of April 2011 (541 tornadoes, 362 killed) characterize the raw natural power and lethality of Dixie Alley.
Interestingly, the region has less often been a source for tornadic research than Tornado Alley and perhaps for good reasons. Limited ground visibility from tree density and hilly, shifting roadways make ground observation as logistically challenging as it is dangerous. Still, some research is finally starting to break through that could help us to understand why this radical increase of tornadoes has occurred and how to protect communities from them.
One of the age old myths of tornadoes is that they are more likely to strike mobile homes or trailer parks than they are to hit a city. Though this is obviously false, the myth is drawn from some true data. While tornadoes form wherever the atmospheric conditions will allow them, they happen to occur frequently in the south. This region just so happens to be highly populated by mobile and trailer-based homes. Though this in no way “attracts” tornadoes, it does invite tragic destruction. The fatality rate is approximately twenty times higher in mobile homes than in permanent structures. Due to the lack of proper foundation, structure quality, and often distance from or complete lack of safe shelter area in these mobile home communities are far more vulnerable to meteorological threats. However, this does not mean that simply living in a permanent structure guarantees safety. Less than 25% of permanent structures in the US have a tornado-resistant structure on the premises. But no matter the location, an accurate warning along with education and preparedness can be life-saving.
Your local National Weather Service Agency releases Tornado Watches/Warnings to inform citizens of potential or imminent risk. The goal is to prevent destruction of life and property as quickly and effectively as possible. These warnings have become increasingly successful with the growth of the internet and data distribution. The NWS has preferred to take an over-cautionary approach when informing residents. On average, warnings result in false alarms 75% of the time. Often, local tornado sirens will be triggered without a confirmed visual at all, but the potential risk is enough to release a warning.
The fundamental challenge to verifying a tornado touch down is that it must be done on-site, either by ground or aerial observation (not satellites or radar). The NWS estimates its records comprise roughly 75% of all tornadoes annually. The reality is that many tornadoes occur in unpopulated areas such as wilderness or cropland, meaning they lack the necessary visual confirmation to record it. This only further skews the warning data toward perceived false alarms.
Unfortunately, this creates a mentality for families to second guess and not take proper precautions for the storm. It’s effectively limit damage through warnings if families don’t buy in to the severity of the situation. The NWS, however, took steps to address this challenge. In 2008, a more precise warning system was implemented that is unique to every event. Previously a whole county would receive a tornado warning, even if half its citizens were in no danger whatsoever. By addressing each storm individually and locally, the NSW hopes to increase the validity of its warning systems to prevent harm to residents.
Though ground-level research in Dixie Alley is tedious and risky, other tools in development may be able to shed light on the explosive growth of tornadoes in the region. NOAA (National Oceanic and Atmospheric Administration), through its VORTEX (Verification of the Origins of Rotation in Tornadoes Experiment) program, aims to research the American Southeast exclusively this year to gain a better knowledge of these storms. Stationed at the University of Alabama – Huntsville, NOAA scientists gather atmospheric data to try and anticipate these severe events as accurately as possible. Then, remote recording instruments are placed along the projected path of a given storm to record data. This information is then validated with sounding data gathered from weather balloons. Though these techniques will surely reveal some of the most intricate tornado data yet, the same challenges of tree cover and topography will continue to make Dixie Alley one of the most volatile natural research regions in the country.
Due to its proximity to the Gulf of Mexico, constant streams of warm, moist air enable the formation of tornadoes in Dixie Alley before and after the “tornado season”. Rather the extent of tornadic activity stretches and migrates fluidly through annual cycles. Starting near the Gulf Coast in late February/early March, tornado spawning zones shift northwesterly in the central plains by spring and summer. As the season begins to slow and cooler air inundates the continental interior, tornadic systems migrate back southward, where they will eventually hit a low point over winter. But this does not mean that Dixie Alley tornadoes cannot occur in winter.
Over the Christmas holiday in 2015, a tornado outbreak tore across Mississippi and Tennessee and reached even as far north as Illinois. A large low pressure system swept across the country, bringing snow to many areas. However, at its southern edge, the system was fueled by enough warm air to produce 55 tornadoes that killed 23 and injured many others. This late December storm ended up accounting for the majority of tornado related deaths for the year. On December 26th the system created its largest tornado, an EF-4 that tore through northeast Dallas. It was only the third EF-4 to occur in Dallas since 1927, and a sobering reminder that these systems can occur anywhere, anytime given the right conditions.
As we begin to learn more about Dixie Alley and the tornadic monsters to which residents have grown all too accustomed, many more challenges are uncovered. As the population of major southern metropolises, such as Atlanta, Nashville, and New Orleans, continues to increase, more residents may find themselves in harm’s way. Additionally, scientists continue to assess the long-term meteorological consequences of climate change. It’s very likely that severe, tornadic storms will continue to increase in frequency and potency, continuing the trend seen in recent years in Dixie Alley.
Together, these challenges only make clearer the necessity for effective warning and education programs along with community and individual preparedness. The secret is out; tornadoes don’t care where or when they strike, but in Dixie Alley, it’s safe to assume they’re not going away any time soon. The only thing that can change is how we deal with them.