Thursday, April 04, 2013

1974 Super Outbreak - A Deadly Anniversary


Today marks the end of the 39th anniversary of the 1974 Super Outbreak, where 148 tornadoes in 13 states (and Canada) killed 319 people over a 24-hour period.  This grim record stood up until 2011, when the Alabama Tornado Outbreak killed 325 people over the same time period.  Out of all the tornadoes, the Xenia, Ohio tornado, rated an F5, is one of the most notable in meteorological history.

Like the 2011 Outbreak, this outbreak was actually foreseen many days in advance.  By April 1st, a
large low pressure system set up across the middle and lower Mississippi Valley.  With a sharp contrast of temperatures ahead of and behind the system and unusually moist air feeding the storm from the Gulf of Mexico, the storm grew exploded.  A smaller outbreak occurred April 1st and 2nd in the lower Ohio Valley.  Forecasters did anticipate a bigger outbreak over the next 36 hours, but not to the extent that had actually occurred.  Severe weather watches were issued in a timely fashion, but still the loss of life was greater for many reasons.  Many towns in the Ohio Valley and into the southeastern US didn't have tornado sirens, and therefore residents didn't receive the warnings.  A common thought at the time was that tornadoes won't cross mountains - which they did - or won't hit more metropolitan areas - which the did.  Cities such as Louisville, KY, Cincinnati, OH, and Huntsville, AL were all impacted by a tornado.

The town of Tanner, Alabama was hit twice during this outbreak, by two separate F5 tornadoes.  Many structures that were merely damaged by the first twister, were destroyed by the second.  Rescuers who were searching the rubble for survivors were sent scurrying for cover as the second one bore down.  One man who was injured after the first tornado sought shelter ahead of the second one.  The shelter he was in collapsed and he was killed.

One of the most famous tornadoes of the outbreak was the F5 that went through Xenia, OH.  One of
the TV stations that serve the town recognized the "new" technique for picking out a tornado's location but looking for it's hook echo.  The TV station then sounded a warning.  As the monster ripped through the town, the Xenia High School was directly in it's path.  Some students were inside practicing for a play, and they sought shelter minutes before the twister hurled a school bus onto the stage.  34 people in Xenia were killed, over 1,000 injured.  Half the town's buildings were damaged or destroyed.  While making a visit, President Nixon described the magnitude of the damage "the worst I've ever seen", even after he toured Hurricane Camile, Hurricane Agnes and the earthquake in Anchorage.

What we learned from this Outbreak helped to change the way the National Weather Service warns for tornadoes, how towns prepare and warn residents, and how we forecast for severe weather.  This type of outbreak was so devastating because of "long-lived, long-tracked" tornadoes.  These words and this description was repeated again and again while telling residents of the 2011 Alabama Outbreak of the dangers that lie ahead.  Both events were very similar, in that most tornadoes followed an overall line, with one giant supercell that spawns several tornadoes over hundreds of miles.  In all, the record outbreak will remain in history as one of the deadliest weather-related 24-hours in US history.