by This winter’s record warmth provided the key ingredient for a Midwest outbreak of deadly tornadoes and destructive hail that hit parts of the Midwest on Wednesday and Thursday, tornado experts said.
At least three people were killed in Thursday’s tornado outbreak in Ohio, Kentucky, Indiana and Arkansas, which came a day after large rocks hit Kansas. It’s a little early, but not unprecedented, for such a tornado outbreak that’s usually associated with May or April, but that’s also because of the warmest winter on U.S. and global records, meteorologists said.
“For severe storms to be this far north at this time of year, it has to be warm,” said Northern Illinois University meteorology professor Victor Gensini.
TORNADO recipe
For tornadoes and large hail storms to form, two key ingredients are needed: wind shear and instability, said Gensini and National Severe Storms Laboratory scientist Harold Brooks.
Wind shear, which is when winds blow at different directions and speeds as they rise, is usually around all winter and much of the spring because it is a function of the normal temperature difference that we see across the country, said Gensini.
But instability, which is the warm juicy moist air near the ground that is the signature of summer, is usually missing this time of year, Gensini and Brooks said.
That’s because Arctic air typically turns south in the winter and early spring, pushing the warm, moist air from the south into the Gulf of Mexico, leaving cool, stable air in its place, said Matt Elliott, a meteorologist warning coordinator for the National Oceanic and Atmospheric Administration. And that cool, stable air keeps tornadoes and large hail from forming.
But not this year. There has only been one real Arctic blast this year and that was two months ago, meteorologists said.
“When we’re warmer than normal, we have more warm tornadoes during the winter,” Brooks said. “It’s not necessarily a causal effect, maybe they’re both happening because of the same thing.”
CENTRAL MEDIUM STORE
Hunter Vance, 27, of Lakeview, Ohio, was talking to a friend on the phone when sirens started blaring. So he sought shelter inside his bathtub for 20 minutes. Then he came out to see the devastation.
He remembers the tough weather last year, but not so soon.
“And it’s never been worse than this,” he added.
Gensini has stopped five tornadoes or large outbreaks in the Midwest or Great Lakes area in the past five weeks, which he said is unusual: Wisconsin had its first ever February tornado on Feb. 8; 32 tornadoes, including one a quarter mile from his home on February 27; large hail and a tornado around the Illinois-Iowa border on March 4; the gorilla hail of 4 inches and several tornadoes on March 13 and the tornadoes on March 14 killed at least 3 people in Ohio and hit other places throughout the Midwest.
Tornado activity this time of year is much more common in the South, and what’s happening is “a lot further north than we normally expect,” Gensini said.
NOAA’s Elliott said it might be a little early, but this is around this time of year when serious storms start to build up in the Midwest, but they don’t usually peak until May.
What happened this week is really a typical spring event,” Elliott said.
Even after Thursday, the year is running slightly below normal in terms of the number of tornadoes and tornado deaths, according to NOAA’s Storm Prediction Center. Before Thursday, tornadoes had killed only two people, which is far less than the 15-year average of a dozen before March 14.
The EL NINO factor
What also makes the Midwest outbreaks unusual is the existence of an El Nino, albeit a weakening one. The natural El Nino, a warming of the central Pacific Ocean that changes weather around the world, often results in fewer severe storms in the Midwest, especially in the spring, studies show.
That is not the case.
Gensini, who co-authored one of the studies, and Adam Sobel of Columbia University, who co-authored another, said the El Nino factor is just one of several variables and the odds are only slightly skewed.
Brooks said he doesn’t trust El Nino as a sign of spring.
CLIMATE CHANGE
No one has done the traditional scientific studies that link specific tornado outbreaks to human-caused climate change. There are so many issues that make it difficult, including poor tornado records in the past and tornadoes being small weather events for global climate models.
And among severe weather events such as floods, hurricanes, droughts and heat waves, tornadoes have been one of the worst issues to link to climate change. Maybe there’s something there, but it’s probably only a small factor, Brooks said.
But given how quickly chart-top temperatures and other climate variables have been, Gensini said, “if ever there was a climate change fingerprint on severe weather it would be this year.”
Gensini hasn’t done any formal attribution studies, but he said “if you look at the recent Februarys and Marches in terms of the number of tornadoes, it’s pretty easy to see that a change is happening,” comparing it to effect of steroids on baseball. home runs in the 1990s and early 2000s.
FASTER
Because of other natural climate factors, Gensini said there is a strong chance of another outbreak of tornadoes in the Midwest in late March or early April.
After that, Gensini said it could be a busy tornado spring for the Midwest, but there’s also a chance the Midwest will skip spring and go right into summer in terms of climate and then come die on the storms.
Last year tornado activity was twice the average through April and “then May was completely dead,” NOAA’s Elliott said.
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Assisted by Joshua Bickel of Lakeview, Ohio.
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