1974 Super Outbreak vs 2011 Super Outbreak

[mwenzbauer]

http://www.weather.com/outlook/weather-news/news/articles/tornado-superoutbreak_2011-10-26

Just noticed this tonite (my apologies if it's already been posted/discussed)... interesting comparison of the 1974 and 2011 Super Outbreaks by Dr. Greg Forbes.

 

[Patrick Marsh]

Pictorially, here is a visual comparison I did with an almost complete track map from public information statements:

1974: http://www.patricktmarsh.com/wp-content/gallery/2011images/19740403.png

2011: http://www.patricktmarsh.com/wp-content/gallery/2011images/20110427_compare.png

 

[Jason Haller]

A question I have is how many tornadoes during the 74 super outbreak went unreported or unrecorded due to the lack of coverage. Now a days almost every tornado seems to have eyes on it no mater where it touches down. Even in a populated area where both outbreaks occurred could there have actually been more Tornadoes in 74 that just went unrecorded?

 

[William Monfredo]

Jason,
I'm in agreement with you. Many weak tornadoes touch down briefly in wooded areas and are not recorded, especially 3 or 4 decades ago; even when meticulous surveys are done, many are impossible to verify. Making comparisons between two super-outbreaks is a valid exercise, but yes, comparing the "count" in this case doesn't stand up very well.

 

[mwenzbauer]

It seems that they're pretty comprable... the '74 outbreak probably had more short-lived tornadoes that bring it's number of total tornadoes more in line with the 2011 outbreak... but as Forbes notes, the Fujita ratings are more thorough now, and either some of those '74 tornadoes would be downgraded, or the '11 tornadoes upgraded on the old F-scale...

 

[Mike Johnston]

Aside from the stats, I would love to hear thoughts comparing the overall synoptic setup of these 2 outbreaks. I've read the technical report on the '74 outbreak many times and it seems like it was as close to a perfect setup as one could imagine. The '74 outbreak featured 3 different north/south-oriented waves of convection, whilst the 2011 outbreak was more confined in area. Although not listed as one of the criteria in the article, I think the aerial extent slightly tips the '74 outbreak as the more impressive of the two.

 

[Patrick Marsh]

What's really interesting is that these "mega-outbreaks" outside the plains states have tended to occur once every 4 decades.

1890s was the "Enigma Outbreak"
1930s was the "Dixie Outbreak"
1970s was the "Super Outbreak"
2010s was the "27 April 2011 Outbreak"

All were large outbreaks. All had large loss of life.

 

[Rob Wadsworth]

Patrick, you are suggesting that there is more anecdotal evidence of catastrophic type outbreaks on a 40 year cycle, as opposed to the 7 year cycle that is currently been discussed?

But the loss of life is incidental - isn't it; when considering that it is equally possible for them to occur in a less populated area.

 

[Patrick Marsh]

I'm just pointing out that we keep comparing the latter two events, but in reality, events of this magnitude are thought to have occurred two times before.

 

[William Monfredo]

And what may contribute to the cycle? In my article "Relationships between phases of the El Niño-Southern Oscillation and character of the tornado season in the south-central United States" in Physical Geography 20, no. 5, 413 - 421, I reasoned and warned that the transition from a warm phase to a strong cold phase would be followed by enhanced potential for significant tornadoes in the primary season in the mid-South, including the northern halves of MS & AL. Within the last year or so, Patrick has posted reasoning relating to the switch, too. What years? 1974 and 2011 are fine examples among limited data.

 

[Patrick Marsh]

William, any chance that you can share your paper? You can email me at [email protected] if you are able to share.

 

[Simon Andersen]

1890s was the "Enigma Outbreak"

Just for accuracy this outbreak occurred in 1884. The only significant outbreak I can think of in the '90's was in april 1890 when Louisville got clobbered. Per Wikipedia 24 significant tornadoes occurred. How many of those were violent is uncertain. This is all I can add to this otherwise great discussion. I have noticed a general 5-year frequency in outbreak occurence here, with the usual reservances.

 

[Patrick Marsh]

Just for accuracy this outbreak occurred in 1884. The only significant outbreak I can think of in the '90's was in april 1890 when Louisville got clobbered. Per Wikipedia 24 significant tornadoes occurred. How many of those were violent is uncertain. This is all I can add to this otherwise great discussion. I have noticed a general 5-year frequency in outbreak occurence here, with the usual reservances.

Ahh, thanks for the correction. I was operating from memory and it appears I got the date wrong. =(