Tornado Alley shifting?

[Dan Robinson]

There is abundant data from a wide variety of sources. These two maps from the University of Nebraska-Lincoln High Plains Regional Climate Center show all tornado reports (left) and violent tornado tracks (right) from 1950 to 2005:

Also refer to Jon Davies' blog post listing the top ten worst tornado outbreaks in US history, ALL outside of the Plains (aside from a small part of the May 1927 event clipping the central Plains):

http://davieswx.blogspot.com/2011/04/27-april-2011-tornado-outbreak-stunning.html

The South matches the Plains on every count - violent tornado frequency, number of tornadoes, tornado damage and deaths. A search for the following terms will also be an eye-opener for anyone still romanticizing the Plains' exclusivity on "tornado alley" and chaseability:

Illinois tornado

Alabama tornado

James Spann might even have the edge on Gary England when it comes to the number of events he's covered live that have affected the Tuscaloosa/Birmingham viewing area.

http://www.youtube.com/results?search_query=abc+33+40+tornado+live&aq=f

The Plains' claim to fame is the regularity and concentration of activity from April-June in mostly better terrain - but the region is certainly not exclusive or even very remarkable when it comes to tornadoes in the South.

 

[Mark Sefried]

It must be global warming that is causing the shift!! Blame everything on global warming.... :~) On a serious note though I don't know the exact stats or anything like that however it seems like in severe drought years across the Plains (like this year) dry lines tend to set up further east than what they typically would in an average year. This usually means areas like Western KS, Western OK, and the TX panhandle just sit and bake under the hot dry sun while Eastern KS, Eastern OK and even far Western MO get slammed. The activity of course shifts further northward with the jet stream as we get into the summer months.

 

[Scott Weberpal]

http://news.discovery.com/earth/redefining-tornado-alleys.html

"Results from this analysis indicate that Dixie Alley has the highest frequency of long-track F3 to F5 tornadoes, making it the most active region in the United States," Frates concluded. Dixie Alley had a frequency value of 2.92, followed by Tornado Alley (2.59), Hoosier Alley (2.37) and Carolina Alley (2.00).

"Based on this analysis," wrote Frates, "colloquial tornado alley fails to represent the areas of highest activity in the United States," a subject he suggested the National Weather Service might want to take up.

 

[Brett Roberts]

There is abundant data from a wide variety of sources. These two maps from the University of Nebraska-Lincoln High Plains Regional Climate Center show all tornado reports (left) and violent tornado tracks (right) from 1950 to 2005:

Also refer to Jon Davies' blog post listing the top ten worst tornado outbreaks in US history, ALL outside of the Plains (aside from a small part of the May 1927 event clipping the central Plains):

http://davieswx.blogspot.com/2011/04/27-april-2011-tornado-outbreak-stunning.html

The South matches the Plains on every count - violent tornado frequency, number of tornadoes, tornado damage and deaths. A search for the following terms will also be an eye-opener for anyone still romanticizing the Plains' exclusivity on "tornado alley" and chaseability:

Illinois tornado

Alabama tornado

James Spann might even have the edge on Gary England when it comes to the number of events he's covered live that have affected the Tuscaloosa/Birmingham viewing area.

http://www.youtube.com/results?search_query=abc+33+40+tornado+live&aq=f

The Plains' claim to fame is the regularity and concentration of activity from April-June in mostly better terrain - but the region is certainly not exclusive or even very remarkable when it comes to tornadoes in the South.

Perhaps Plains tornadoes are "romanticized" because they and their parent storms are simply of far better quality, for chasers, than most of those outside the Alley?

I doubt that many meteorologists or even hobbyists would argue that the Midwest or South fail to compete with the Plains in pure annual tornado count. Your argument makes plenty of sense in that regard. Where it doesn't make sense, to me, is from a chaser's perspective. I realize that the Plains have become overrun with chasers, amateurs, and clueless locals alike, making it awfully tempting to convince oneself that less-popular areas are hidden gems of sorts. Believe me, I wish I could agree with you there. But as someone who appreciates structure, visibility, and discrete storms, I can't bring myself to do it. And this year has really made me try!

I suppose a lot of it comes down to whether you consider yourself a "storm chaser" vs. a "tornado chaser." If the latter, then sure, I totally understand the appeal of IL/IN, or even MS/AL; many have found success there already this year, and without the inconvenience of May 19-like convergence. But if you regard tornadoes as a rare treat, and derive most of your joy over the course of a year from the jaw-dropping sights of explosive, high-CAPE storms with monster hail that just plain look cool, chasing east of the Mississippi becomes a much more difficult affair. Outside of extraordinary setups like Super Tuesday or last week's outbreak, I can't find it in me to justify the expense and time to make the haul out east, knowing that intercepting a tornado as it crosses the tree-lined road ahead of me is practically the *only* way my trip will redeem itself. Others are free to make that call for themselves, but the bottom line is that the Plains are a disproportionately popular and crowded chasing destination for a good reason.

Disclaimer: last Wednesday broke pretty much all the rules I had for eastern setups, with an abundance of highly-photogenic tornadoes and supercell structure. However, I'd argue the very fact that so many of us were in awe over sights like the Tuscaloosa tornado (what? not rain-wrapped with five-foot LCL's??) and the incredible structure Bill Hark got in VA illustrates my misgivings about chasing "typical" setups out there quite well.

 

[Dan Robinson]

making it awfully tempting to convince oneself that less-popular areas are hidden gems of sorts. Believe me, I wish I could agree with you there. But as someone who appreciates structure, visibility, and discrete storms, I can't bring myself to do it.

That's just the thing - the less-popular areas are indeed hidden gems in the sense that the meteorological parameters come together in these regions at least as regularly as they do in ND, SD and MN for example - and they do produce. I'm not suggesting these regions are better than the Plains in terms of frequency, just equally viable when the ingredients are there. That can be said for any location. I could have had a tornado near Pittsburgh in March because I saw the potential. It was simply the financials that prohibited the long drive, not the territory.

For the average Plains chaser, there is a prejudicial rejection of setups in the Midwest and South as unchaseable or unphotogenic, when we have evidence on the rise every year (due to increased coverage) that shows this isn't exactly the case. Many refuse to chase in these regions on principle, regardless of the merits of any setup there. That's the main thing I don't understand. One doesn't have to dig far to find images of great structure, photogenic tornadoes and large hail in the Midwest - most years it isn't unusual to have 1 to 3 days like 4/19/11 and 6/5/10 somewhere east of the Mississippi.

And while a large percentage of Plains terrain/roads is indeed ideal, chases in problem areas exist more often than we'd like to admit. Northwestern OK (Canadian River), northeastern TX Panhandle, Cherry County NE and vicinity, east of I-35 in OK. Rarely is a good setup bypassed in these areas, though. And not every Plains setup produces highly photogenic storms - a Mulvane or Campo day definitely isn't the norm.

I can somewhat understand an OK, KS or TX resident, either cash-strapped or having a great season at home hesitating to drive 6-12 hours to IL, IN or IA. But the same faction will often drive to SD/ND during a 2006-like year. And someone on a chase vacation, with the ability to travel anywhere, ditching a good setup in the Midwest or South in favor of a weakly-sheared, low-cape dryline day in Texas is confusing. Given a similar good setup in ND/SD/MT/WY, an equal or even longer drive is commonly made by virtue of the location being in the Plains, and less by virtue of its meteorological offerings.

4/19 was a good case in point. Particularly given the lackluster Plains season so far, by what decision criterion did most Plains chasers decide not to target MO/IL? Because it was MO/IL, that's why. The merits of the setup didn't override that prejudice for most. And I was glad, as I got to watch an amazing tornado on the open prairie with no human being around me for at least a mile in all directions. It was the second time that happened to me (take a guess in what state the first happened).

My main point isn't to trash or downplay the Plains - it is an amazing place to chase, but isn't the only good place to chase when a setup comes together.

 

[Robert Dewey]

Here's a map of violent tornadoes [>=EF4] from 1950-1980 [30 years] (gray), overlaid with 1980-2005 [25 years] (red). I think an overlap indicates pretty good hot zones (you could probably break it down further on a decadal basis). Some areas seem to be flukes, or skewed by single outbreaks that overachieved. For example, here in SE MI we averaged violent tornadoes just about every 10 years from 1950 to 1980 across 6 different outbreaks... but haven't experienced one since. Perhaps the Fujita scale was more liberal back then?

The central plains definitely look more consistent to me, at least from OK through NE eastward into IA... along with the deep south (MS / AL).

 

[CZandbergen]

And while a large percentage of Plains terrain/roads is indeed ideal, chases in problem areas exist more often than we'd like to admit. Northwestern OK (Canadian River), northeastern TX Panhandle, Cherry County NE and vicinity, east of I-35 in OK. Rarely is a good setup bypassed in these areas, though. And not every Plains setup produces highly photogenic storms - a Mulvane or Campo day definitely isn't the norm.

I guess it is all a matter of taste. Living in Tulsa and having the opportunity to chase whenever I like, my chase partner and I usually let anything east of I35 or south of I40 go as far as chasing. It isn't that you can't score a great storm, it is just that it isn't as enjoyable as catching one exposed like they are north and west of Enid. There is a different rhythm when you get out on the plains to chasing in the jungle. I agree with what others have said about chasing in CO, NE and even SE WY as well. Sure every area has its issues, but on balance I would rather chase in an area with a good road network and good visibility. You can't let a once in a hundred year outbreak in the SE color your judgement. Some of the best video there was shot on tower cams. Others scored good footage as well, but again, on balance I have no idea why anyone would want to chase anything east of where I live, and I don't like to chase anything at least two hours west...

 

[Michael Gavan]

Here's a map of violent tornadoes [>=EF4] from 1950-1980 [30 years] (gray), overlaid with 1980-2005 [25 years] (red). I think an overlap indicates pretty good hot zones (you could probably break it down further on a decadal basis). Some areas seem to be flukes, or skewed by single outbreaks that overachieved. For example, here in SE MI we averaged violent tornadoes just about every 10 years from 1950 to 1980 across 6 different outbreaks... but haven't experienced one since. Perhaps the Fujita scale was more liberal back then?

The central plains definitely look more consistent to me, at least from OK through NE eastward into IA... along with the deep south (MS / AL).

One thing that's always stood out for me is that Michigan hasn't had an EF4 or greater since the mid 70's, but had many of them before then. Long overdue. I think 'Tornado alley' does shift based on El Ninx, the PDO and other factors like drought in the SE or S/C US.

 

[Wes Carter]

Several people have mentioned the lack of chaser convergences in the Southeast and Eastern US in general. Although that is true to an extent, there is still much more traffic to contend with coupled with fewer areas to safely pass on two lane roads. But as Dan mentioned, there are some areas that are chaseable. I like chasing anywhere along the Mississippi River for the most part, Northern Alabama west of Huntsville, much of Western Kentucky, and almost all of Illinois north of I-70. Otherwise, it is challenging to chase fast moving storms with low LCL's along roads with trees on both sides that can curve at any time and take you right into a dangerous area, or into a little town with a 20mph speed limit. Out here, you just have to find a good viewing area, pre-position yourself, have an escape route, and hope you chose well.