This winter’s record warmth provided the key ingredient for a deadly tornado outbreak in the Midwest and damaging gorilla hail that hit parts of the Midwest Wednesday and Thursday, hurricane experts said.
At least three people died in a tornado outbreak that hit Ohio, Kentucky, Indiana and Arkansas on Thursday, a day after large hail hit Kansas. While it’s a bit early for such a tornado outbreak, which is typically associated with May or April, it’s not unprecedented, but it’s also the warmest winter on both U.S. and global records, meteorologists said.
“The weather needs to be warm for severe storms to occur this far north this time of year,” said Victor Gensini, a meteorology professor at Northern Illinois University.
HOSE DESCRIPTION
Gensini and National Severe Storm Laboratory scientist Harold Brooks said two key ingredients are needed for large hail tornadoes and storms to form: Wind shear and instability.
Gensini said wind shear, which means winds blow in different directions and speeds as elevation increases, typically occurs all winter and much of the spring because it’s a function of the normal temperature difference we see across the country.
But Gensini and Brooks said summer’s signature instability — slushy, warm moist air near the ground — is often missing this time of year.
That’s because normally in winter and early spring, Arctic air dips south, pushing warm moist air south toward the Gulf of Mexico and leaving dry, stable cold air in its place, said Matt Elliott, National Oceanic’s warning coordination meteorologist. Atmosphere Management. And this cool, stable air prevents tornadoes and large hail from forming.
But not this year. There has been only one true Arctic blast this year, and that happened two months ago, meteorologists said.
“When we’re warmer than normal, we tend to get warmer hurricanes during the winter months,” Brooks said. “This isn’t necessarily a causal effect; maybe they’re both due to the same thing.”
STORMY MIDWEST
Hunter Vance, 27, of Lakeview, Ohio, was on the phone with a friend when the sirens started blaring. So he took shelter in the bathtub for 20 minutes. Then he went out to see the destruction.
He remembers last year’s severe weather, but not this early.
“And it’s never been worse than this,” he added.
Gensini pointed to five tornadoes or major outbreaks in the Midwest or Great Lakes region in the past five weeks, which he said are unusual: Wisconsin gets its first tornado of February on Feb. 8; 32 tornadoes on February 27, including one within a quarter mile of his home; Large hail and tornadoes on the Illinois-Iowa border on March 4; 4-inch gorilla hail and some tornadoes on March 13, and tornadoes on March 14 that killed at least 3 people in Ohio and hit elsewhere in the Midwest.
Gensini said tornado activity this time of year is much more prevalent in the South and occurs “much further north than we would normally expect.”
NOAA’s Elliott said that may be a little early, but this is about the time of year that severe storms begin to increase in the Midwest, though they generally don’t peak until May.
Elliott said what happened this week was “a really typical spring thing.”
Even after Thursday, the year remains slightly below normal for tornadoes and tornado deaths, according to NOAA’s Storm Prediction Center. Before Thursday, tornadoes had killed only two people; that was far fewer than the 15-year average of a dozen before March 14.
EL NINO FACTOR
What makes Midwestern outbreaks unusual is that El Niño is present but is beginning to wane. Studies show that natural El Niño, a warming that occurs in the central Pacific and changes weather patterns around the world, generally leads to less severe storms in the Midwest, especially in the spring.
That’s not the point.
Gensini, who co-authored one of the studies, and Adam Sobel of Columbia University, who co-authored another, said the El Niño factor is just one of several variables and changes the odds only slightly.
Brooks said he doesn’t have much faith in El Nino as a signal of spring.
CLIMATE CHANGE
No one has done the traditional scientific studies linking specific tornado outbreaks to human-caused climate change. There are many issues that make this difficult, including poor hurricane records in the past and the fact that hurricanes are minor weather events for global climate models.
Along with all severe weather events such as floods, hurricanes, droughts and heat waves, hurricanes have become one of the most challenging problems associated with climate change. Brooks said there could be something there, but it’s probably just a minor factor.
But given that temperatures and other climate variables are off the charts, Gensini said, “If there was a sign of climate change in severe weather, it would be this year.”
Gensini did not conduct any formal attribution studies but said “if you look at last February and the Marches in terms of the number of tornadoes, it’s pretty easy to see that a shift has occurred” and compared it to the impact of steroids on baseball. Home runs in the 1990s and early 2000s.
MORE COMING SOON
Because of other natural climate factors, Gensini said there’s a high likelihood of a new tornado outbreak in the Midwest in late March or early April.
After that, Gensini said, there could be a busy spring of hurricanes for the Midwest, but there’s also a chance the Midwest could skip spring and move directly into summer in terms of climate, and then the storms would subside.
NOAA’s Elliott said last year’s tornado activity was twice as high as average through April, and “May was completely dead.”
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Joshua Bickel contributed from Lakeview, Ohio.
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