Wondering what your thoughts are on this trend of tornadoes apparently "migrating" eastward over the last few decades. I know the article mentions climate change as a possible explanation. Do you think this is the most likely reason, or could there be other factors? If so, what? I've attached the link to the WLFI version of this news story below.
Thank you for your question Josiah!
Such migrations of highest tornado occurrence have been around for multiple decades, even centuries to thousands of years.
Many factors drive it, especially strength, position & duration of a La Nina or El Nino. There are even types of La Nina & El Nino, namely Modoki La Ninas & Modoki El Ninos. This in combination with PNA, PDO, AMO, etc............all of these indices drive weather patterns over a period of time & some patterns are a decade long before shifting. They may go into their warm or cold phase cycle for 5-10 years, then flip. Some even stay in a certain phase longer before flipping. It also is driven by drought in the Plains & western U.S., but even that is tied to all of these other indices. In turn, the continued rise in CO2 & absence of sunspots may impact any one of these indices, as well.
So, it is more natural in occurrence for these allies to move, but you cannot ignore that CO2 is the dark horse that is making certain weather events a bit more unpredictable. I have watched patterns that show extremely high probability for cold here turn out much milder & I cannot pinpoint the exact factor at times. The analogs are having trouble with this +400 ppm CO2. It is driving things we do not understand that did not affect our weather so much 100 years ago.
In the 1880s WE were the hot spot for tornadoes. There were more violent tornado outbreaks in Indiana in the 1883-1888 period than any other since 1850. Tornadoes in the 1880s tended to be violent when they occurred & spurred the American Red Cross & led to the formation of the Mayo Clinic.
May 1883 & May 1886 are two noteworthy historic outbreaks for Illinois & Indiana. This all occurred with dry line shifting eastward amidst a string of La Ninas. These were also historically cold, snowy winters with a high degree of lingering cold air aloft left late into the spring, apparently. There were also several significant volcanic eruptions in the 1880s.
In the 1930s, the dry line would tend to shift way east, so there were more tornadoes east of us & south of us. However, this was the derecho decade with several historic derechoes hitting the region in the summer on the periphery of the intense heat waves in the Plains & Midwest. These were the only rain makers of any reasonable extent during the worst droughts of the 1934, 1936 summers. Even 1933 & 1938 saw substantial summer derechos in the region.
Violent outbreaks returned to the Plains in the 1940s.
In the 1950s it was Northern Plains & Lakes to the Northeast U.S.
In the 1990s, it was the Plains to Midwest, largely, that caught the outbreaks.
In the late 2000s to early 2010s, the shift of violent tornadoes was to "Dixie Alley" in the South, but that belt has since waned.
Here in 2018, it has been Iowa to Minnesota, Wisconsin & Michigan that have seen the bulk of tornadic activity, though there has been a lack of violence with the events & outbreaks.
In 1845, a highly-unusually, significant long-track supercell storm produced a massive violent likely EF5 tornado in New York's Adirondaks in September. Other violent tornadoes occurred as far north as Ontario & Quebec to Vermont. These years of the mid 1840s saw many tornadoes of impressive violence & duration in the Northeast. Drought was apparently prevalent over the Ohio Valley & Midwest 1845 & 1846.
It was in 1854, as well, when a rare, violent likely EF4 tornado tore through eastern Ohio in January with temperatures around 70 degrees. Other tornadoes occurred on the same day with wind damage & hail as far west as New Harmony, Indiana & Indianapolis. Tornadoes were also reported in the morning hours near Crawfordsville & Rochester. 1852-1856 saw massive drought in the Plains & into the Midwest. It peaks as far east as New York in summer 1854. The drought peaked in our area in 1854 & 1856. There was a lack of tornadoes & severe weather reported in the 1853-57 period in our area & region, but much from eastern Ohio to the East Coast.
So, this is a phenomenon that has been around for a while & will continue.