Updated 2/14/2020
A few weeks ago, a study was published saying that tornado alley - N TX thru S ND into E CO, W AR, SE WY & SW MO - is seeing fewer tornadoes and the climatological (30 yr) epicenter of tornadoes is shifting eastward. Several rumors/ innuendos/ stories/ and hyped-up statements have emerged. But I think several factors are at play here.
Errors?
The first thing we need to look at to dispute this is potenital for error. Thirty-year climatology for tornadoes for the 1960-1990, 1970-2000, 1980-2010 and soon-to-exist 1990-2020 periods will capture most tornadoes thanks to advancements in radar capabilities. Some tornadoes are still missed due to population density - cited by Dr. Nese & Dr. Forbes (both were at Penn State) in their 1998 article on PA tornado climatology, an intense study of PA tornadoes in 1996 found at least one tornado that would have been classified as straight-line wind damage. However, these missed tornadoes, even on a national scale, do not provide a huge error to the results (at least not as huge as before 1960 or especially before 1990). NWS now surveys the worst damage whether or not a tornado was sighted and pictures on social media also help NWS (the claims can be a problem). For instance:
Lingonier, MA in Aug. of 2015 was hit by a supercell and a very ominous cloud - sent through social media. The supecell had a hook on radar but a survey found no tornadic damage. Why didn't one form? Not enough moisture. I was watching the radar live from the AMS Mesoscale Conference in nearby Boston at the time alongside Howard Bluestein. Yep, the Boston native and Univ. of OK professor frequently cited in the news, professional journals and on video documentaries.
So, with errors out of the way, what is my problem?
Recent Data: Dixie Alley & 2011
The results of the study are 1985-2015 and there were several recent outbreaks in the Southeast states, known as Dixie Alley (think Civil War). Most notable is April 27th, 2011: Alabama was hardest hit. And 2012 was quiet overall but even more so in the Plains states - again, traditional tornado alley. Last year (no reflected in the report) was quiet too but unfortunately for 2-3 dozen people so far, this year is starting active. My condolences to the families.
This is a consideration.
Combining Errors & Recent Data
We also have to consider that the study didn't compare data in large enough increments - change in 25-yr climatology over time: '60-'85, '65-'90...'90-'15. With so much year-to-year variability, I conclude that their study is flawed. It is a trend worth watching.
Further: ENSO, Plains vs. Southeast, and Climate Change
Studies also found a connection between the epicenter and teleconnections. You'll frequently hear that term in seasonal forecasting or you may be familiar with PNA, AMO, SOI (a big factor this winter), QBO, MJO, AAO, NAO, AO, PDO and particularly ENSO (El Nino "Southern" Oscillation) - region 3.4 affects the USA. ENSO's has two phases: warmer than avg (El Nino) or cooler than avg (La Nina). These teleconnections tell us where the shift will occur: somewhat but not exactly where. Using both climate and NWP models, all the scenarios (back to the Plains, staying in the SE and shifting further north & east) do play out in the climate guidance - and it doesn't matter if the future is cooler or warmer (whether human-influenced or natural variability). Again, all scenarios still play out this year and in future years.
Preparation
There are two points I'd like to emphasize. In terms of tornadoes, they have occurred in the history of each of the lower 48 states because the USA has access to all the ingredients for tornadoes. Second, if you are not in tornado or Dixie alley (and even if you are in some of those areas), you are still prone to other disasters that everyone should be prepared for. That's all any of us can do is to be hope for the best and prepare for the possibility of the worst (whether imminent or not). There's no need to panic and it is irresponsible to cause panic when something isn't imminent (severe weather) nor predictable (exact time of major earthquakes for instance). The disaster kits I have you put together (and check when the time changes - just now BTW!) apply to any disaster to which your community is prone. And even if there is something predicted, moving calmly yet steadily will increase your chances of executing your plan (evac, shelter in place, etc.) successfully. Thank you for your time.
