Southeast Tornado Outbreak

The horrific damage and death toll from the April 26-28 tornado outbreak is a national tragedy. At least 350 people died from the outbreak and some reports as of tonight indicate hundreds are still missing. The forecasts for this event were superb and no doubt life-saving.

The National Weather Service for days highlighted the potential for a deadly tornado outbreak in the southeast and issued some of the most strongly worded tornado watches and warnings I’ve ever seen. There were few people in Alabama who didn’t know tornadoes  were coming for several reasons.

  • Exceptionally long-lead and strongly worded watches and warnings (average lead time for tornado warnings in the event was 24 minutes).
  • Tornadoes in Alabama occurred during the afternoon and not at night while people were sleeping and unaware
  • Dramatic LIVE video of tornadoes on the ground by local TV stations

On the contrary, it is possible that some people without power from earlier storms, may have been caught off guard. Most people, however, seemed to have known violent tornadoes were moving toward the region. This storm did not strike without warning.

Still this tornado outbreak, rivaling the Super Outbreak of April 3-4, 1974, will go down as one of the most deadly in United States history. This is the deadliest tornado outbreak since April 5-6, 1936 and the deadliest single day for tornadoes since the Tri-State Tornado on March 18, 1925.

What makes this outbreak and the death toll so tragic is that many of the dead likely knew the tornadoes were coming and were sheltered.  Here’s a radar composite of the supercell that produced the long track and violent tornado through Tuscaloosa and Birmingham.  (Courtesy: Brian Tang/NCAR)

It appears that some of the deaths were from people who sought shelter but the tornado was too violent and swept homes clean off their foundation, making survival difficult. It should not be a surprise that violent tornadoes make up only a small fraction of all tornadoes (less than 1%) but are responsible for over 70% of tornado related deaths.

The odds of a tornado hitting any one home are quite low (much, much lower than a hurricane in Alabama, for instance) . The odds of a violent tornado strike (EF-4 or EF-5) are minuscule. While most violent pass over sparsely populated regions this  tornado struck a moderately densely populated area and was on the ground for a long time making the damage and death toll so horrific.

In my opinion there is little that can be done to protect people in the path of the most violent tornadoes short of “safe rooms” or communal shelters in neighborhoods (likely cost prohibitive).  Evacuation is virtually impossible given current warning lead times and could lead to the potential of even more casualties as people are stuck in traffic fleeing a tornado.

As bad as the final toll will be in Alabama and surrounding states this event is not a “worst case scenario”. My college professor Yvette Richardson co-authored a journal article several years ago Low-Level Winds in Tornadoes and Potential Catastrophic Tornado Impacts in Urban Areas. The research is astounding.

“Simulated tornadoes with wind field structures similar to those observed, and potentially worse plausible tornadoes, crossing a densely populated urban regions such as Chicago, could cause widespread damage and loss of life on a scale that has not been observed historically with tornadoes.”

The findings show that the largest and most intense tornadoes (likely similar to the EF-5s  in Alabama and Mississippi) could “completely destroy structures across more than 90 sq. km, killing perhaps 10% of the residents in these structures, resulting in as many as 13,000-45,000 deaths in densely populated cities such as Chicago.”

The storms in Alabama show the impact of a violent tornado crossing a somewhat densely populated region but one day a tornado of equal or greater strength will impact a more densely populated region.  Had the Tuscaloosa or Birmingham tornado struck at night or with less warning lead-time the casualties probably would have been higher.

The cleanup will go on for weeks, months, and years. Hopefully the meteorological community will learn from this event and in particular if there are ways to mitigate the loss of life from violent tornadoes in densely populated areas.


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