Andy Wehrle
EF5
Based on the time given I think that's the Pisgah-Flat Rock-Trenton (GA) EF4. The Rainsville EF5 took a path parallel and a little south, a few hours later.
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Based on the time given I think that's the Pisgah-Flat Rock-Trenton (GA) EF4. The Rainsville EF5 took a path parallel and a little south, a few hours later.
Tim Paitz
EF2
Shear and helicity were off the charts and there was rather high CAPE of 2500-4000 J/KG as well.
Kevin Bowman
EF4
JamesCaruso
Staff member
I have been reading the book "What Stands in a Storm" by Kim Cross and it prompted me to revisit all 29 pages of this thread. I was surprised about the discussion as to whether there was anything unusual about the synoptic environment to yield such an event. Of course I realize there are many events forecast to be outbreaks but do not come to fruition. But I thought this one was known to be an unusually favorable setup, hence the significantly elevated degree of alarm in the forecasts that preceded it? Just wanted to better understand this issue and also see if, now five years later, there is any further clarity about it, including any papers that you guys might recommend, such as analogous to the one on '74 linked to in Jeff's post above.
Jeff I am quoting your post because I know if you see it you'll respond
But would love to hear from others as well (I saw Rich Thompson had also posted about this).
A couple of asides...
First, sad to see that so many of the links in this thread are broken - goes back to what Dan Robinson and others have recently lamented. Indeed seems like some historical curation has been lost. Sure, there is plenty of documentation of the event in other places, but here it was interesting to go back and experience the immediacy of it, because it was connected to the time of the event and all of the emotion and uncertainty; it was amazing to see the aftermath as viewed through the lens of chasers struggling to make sense of it all as the enormity of the tragedy became clear. But without many of the links this aspect of the event's history is less than it otherwise could be. I am glad to see many of the links are still valid five years later, but will that be the case in another five years, or 10?
Lastly, I am not yet done with the book cited above but it has been a compelling and emotional read. Despite a few meteorological inaccuracies that I could nitpick, the author does a fairly good job of setting up the event in such a way that even as a chaser I could read it without rolling my eyes; she certainly sets up a sense of doom. And then reading about the aftermath is absolutely heartbreaking. Just an unspeakable and unimaginable amount of human suffering, sorrow and loss. Similar in that regard to "F5" by Mark Levine, which I read a few years ago. But the multiple occasions of parents having to identify their children after they were killed near U of A in Tuscaloosa, man that was tough to read, much more so than "F5." You can't have children of your own and not literally be in tears reading parts of this book. I certainly was...Brad Dormer
EF1
Reading through this for the second time this month makes me wonder where and when this could happen again and if it could be worse. We haven't really seen a tornado outbreak nearly as severe as this since it happened, and lots of areas are definitely long overdue, especially in the Kansas/Nebraska/MO/IA areas, living in these areas (basically the heart of tornado alley) and being 15, I still haven't seen a significant outbreak in my area and I'm wondering if it could happen soon.Boris Konon
EF3
Of course it will happen again, given enough time. From the limited good data period we have, it does not seem to be a common event.
We went 37 years between Superoutbreaks 1974 to 2011, but that's only two data points. Since tornado documentation declines
quickly prior to the 1950s, it's hard to really know the real frequency of such large and intense outbreaks. Prior to 1950, there is
evidence of outbreaks on the 1974 and 2011 scale, but on paper they do not look that impressive, at least in terms of the
number of tornadoes in each outbreak. Many violent tornadoes do show up well in this period, but even some of those were very
likely missed. Most focus in those days were on tornadoes that hit populated areas.
If another Superoutbreak occurs say in the next 10 years, that still does not give us any real pattern, nor is it a "sign" of anything.
When dealing with events that only occur once every several decades or more, you need a much longer period of solid, reliable records
to get any real sense of how often these occur. In this case, at least 150 years of good tornado records is likely needed.
Andy Berrington
EF2
There are several issues with getting outbreaks of this size W of the Mississippi River. One is that any sort of significant westerly component to the low level winds tends to advect dry air from Mexico rather than the Gulf of Mexico given the geography of the US (4/11/65 occurred with a SW/WSW LLJ, which wouldn't work in the Plains). These bigger events often occur with large scale upper level systems that tend to be going through their mature phases at the times of the outbreak. Often troughs that produce events in the Plains are still in their developmental stages (unless they're already swinging out negatively tilted, in which case their strong forcing for ascent often leads to what I'll elaborate on below).
You also need a rather broad area of moderate large scale ascent and moderate capping present to initiate multiple storms in the warm sector/along confluence axes, keep prior convection to a relative minimum to allow significant destabilization and not initiating too many storms to have a quick transition to linear (which is why more broad cyclonic flow like 4/3/1974 is favored vs highly amplified/sharp configurations). Plains events often only have one or two initiation sources (usually the dryline being one of them). Because of the proximity of the Plains to the EML source region, you often have quite strong capping during the afternoon prior to initiation with Plains events, and thus you need quite strong forcing for ascent to initiate storms. This often leads to storm modes becoming messy after the first few hours (see 5/24/11 or 5/10/10 for prime examples). If you don't have that strong large scale ascent, you'll wind up with only isolated cells or a cap bust.
There aren't many cases I can think of where you had that "sweet spot" of moderate ascent and a moderate cap in the Plains. Ones I can think of right off the bat would be 5/3/1999, 3/13/1990 and perhaps the outbreaks of April 22 and April 27, 1912 for the Southern Plains. For closer to your region, March 23rd, 1913 is probably your benchmark for NE especially. But even these events aren't on the same level as some of the monsters further east like 4/27/2011, 4/3/1974, 4/11/1965 and 3/21/1932.
I guess what I'm saying is, it's not impossible, but it's more unlikely over your region than it may be over the Great Lakes/Ohio Valley/Southeast.
Andy Wehrle
EF5
I'm curious, has anyone done a comprehensive storm-by-storm analysis of each supercell in this outbreak and the tornadoes it produced (a bit like the one done for 5/3/99, "Storm A," "Storm B," etc.)? The Wikipedia tornado list is an excellent resource but doesn't break them down by storm:
https://en.wikipedia.org/wiki/List_of_tornadoes_in_the_2011_Super_Outbreak#April_27_event
You have to infer, for example, from the times and locations that the storm that produced the first significant tornado of the afternoon outbreak, an EF3 that began at 1836 UTC (1:36 PM CDT) near Oxford, MS, later produced an EF0 tornado at 1928 UTC in Union County, MS before either dissipating or being absorbed into another storm.Jeff Wright
EF4
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