© 2019 Terry Swails

41 YEARS AGO, THE DAY THAT SHAPED ME AND FORECASTING

April 3, 2015

April 3-4th. 1974 is a day I will always remember. I was a senior in high school and fascinated by tornadoes. I would read anything I could get my hands on related to the subject. One of the things that was difficult to find were pictures, especially videos of tornadoes. However, that all changed for me following this incredible outbreak.

In 1974 , video cameras were becoming popular at a reasonable price. Many Americans had them and they were light and simple to use. In the “Super Outbreak” 358 tornadoes dropped from the sky and many were documented by multiple people with video recorders. I clearly remember the compelling videos and the horrific destruction.

MULTIPLE VORTEX ZENIA, OHIO TWISTER

Not only was it a turning point for me and my career in meteorology, it was the catalyst for new techniques in tornado detection and warning systems. The death and damage tolls were so high that the National Weather Service made radical changes that included the installation of next generation radars which were the forerunners of the Dopplers we utilize today. Warning systems were improved and sirens which had limited use in 1974, were installed in communities throughout tornado alley.

 

I came across a nice article by Kathryn Prociv a meteorologist and contributor for the Washington Post’s Capital Weather Gang capsulizing the event. Lot of interesting facts and insights and her work is appreciated.

The “Super Outbreak of April 3-4, 1974” occurred across portions of the Midwest, Lower Mississippi Valley, and Southeast.  In what was the worst tornado outbreak of the 20th century, there were 148 tornadoes over the course of just 18 hours, over half of which were classified as significant/strong at F2 strength or higher.

Many comparisons have been made between this outbreak and the April 25-28, 2011 outbreak which featured 358 tornadoes.  Although the more recent outbreak featured many more tornadoes, they occurred over a longer time period in an age of better tornado detection, and the worst was confined to a smaller area compared to April 3-4, 1974.

Perhaps the most staggering fact from the 1974 outbreak was the amount of F4 and F5 tornadoes; an incredible 30 (23 F4s and 7 F5s).   The 1974 outbreak featured 30 violent tornadoes in less than one daywhen the national average is only about 7 per year.

The chart above displays a comparison of the most intense tornadoes (F/EF3 or higher) between the 1974 and 2011 outbreaks. In all of these categories, 1974 prevails with ease. Tony Lyza provided a more detailed numerical breakdown comparing the number of significant tornadoes between the 1974 and 2011 outbreaks in a post last year.

The April 1974 outbreak has been reviewed, discussed, and analyzed ad nauseum throughout the meteorological community over the years: from the meteorological set-up, to climatological comparisons, to NOAA and National Weather Service reviews.

This article looks at the April 1974 outbreak from a different, visual perspective.  I use maps to first look at the event from the past, then present the same information with a fresh face using some thought-provoking interactions and overlays.

The First Super Outbreak Map Ever Made

The first map ever made of the April 3-4, 1974 event was done by the renowned Ted Fujita when he was affiliated with the University of Chicago.  He personally surveyed most of the tornado paths and produced this hand-drawn map with impressive detail and acuity.

 

Popular Maps of the Event

As already mentioned, meteorologists have been studying this event for close to 40 years.  Below are maps from NOAA and the Tornado History Project that are popular resources and available to the public.  Both maps are great visual representations of the event, as they symbolize the individual tornado tracks rated according to the Fujita Scale.

 

Both maps above provide a good reference of the spatial distribution of the tornadoes as well as distribution of the different tornado strengths.  The greatest concentration of tornadoes occurred over portions of Indiana, Ohio, Kentucky, and Tennessee.

All seven F5 tornadoes occurred on the 3rd, and Alabama was the state that experienced the highest number of F5 tornadoes that day; three out of seven.  The other F5 tornadoes occurred throughout Kentucky, Indiana, and Ohio.  Here is the final confirmed tornado count and breakdown according to Fujita categories:

And here is a chart showing the distribution of tornadoes by state; 13 states total.  Tennessee experienced the most tornadoes out of any other state, with 37.

 

New Perspectives

The first map interaction involves overlaying the tornado tracks symbolized according to the my color scheme above (see legend) on top of Ted Fujita’s original tracks.  Adding the color information helps enhance Fujita’s hand-drawn tracks while still maintaining the historical map feel.

Here is a zoomed in version of the same map:

A second map interaction of interest investigates a “what if this happened tomorrow?” scenario.  In other words, given the current population distribution and the urban sprawl around major population centers what areas would be hardest hit if this same outbreak happened today?

The map below involved overlaying urban areas according to the 2010 Census on top of Ted Fujita’s original track map

While U.S. population has not necessary exploded since 1974, urban sprawl has undoubtedly become more prevalent.  By looking at the map, it is easy to see which urban areas would be devastated if this outbreak occurred today.

On the northern edge of the outbreak Decatur, Illinois and the suburbs of Cincinnati, Ohio are hit hard.  On the eastern edge of the outbreak area Roanoke, Virginia, a city which has significantly expanded both in size and population since 1974, would experience major damage from the tornado that struck the town in the early hours of the 4th.

Moving south across Kentucky, the northern suburbs of Louisville and southern suburbs of Lexington are impacted; these areas of Kentucky were hit hard by the March 2nd, 2012 outbreak. Moving south still, the suburbs of Nashville are devastated by multiple tornadoes.  Finally, at the southern edge, Hunstville, Alabama would likely sustain catastrophic damage from one of the long-track F5 tornadoes.

Here’s a zoomed in version of the map to better see some of the urban areas:

Conclusion

For at least certain benchmarks, the Super Outbreak of April 3-4, 1974 remains as THE tornado outbreak that all other tornado outbreaks are compared to.  April 25-28, 2011 was compared to 1974 in terms of the atmospheric set-up (both occurred in a La Nina pattern) and also compared in the number, spatial distribution, and intensity of the tornadoes.

Given the ferocity and destruction associated with these large-scale tornado outbreaks, tornado researchers wonder if these events will remain as once-in-a-generation events, or if they will happen more (or less) frequently.  In a country that experiences 75% of the world’s tornadoes each year, it is well worth reviewing these big outbreaks on their anniversaries.

I’ve included a link to an old video called Day of the Killer Tornadoes. It’s pretty funky and has some old footage

https://www.youtube.com/watch?v=WOM8SPNGLhY

Well, I’ve been doing TV weather for 39 years and I’ve seen some remarkable things. Historic weather events and technology that has changed the face of television forecasting. The one thing I’ve been incredibly blessed with is the fact a violent deadly tornado has never hit a town in my viewing area. I’ve had them all around me but never in my zone of warning responsibility. I pray every night that the streak continues until I hang up the microphone. Roll weather…TS

 

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