Tornadoes in February? Why That's Not Uncommon
Deadly tornadoes have lashed the United States for centuries. Most of the worst occurred before modern warning systems existed, although one occurred almost exactly two years before the deadly twister that struck Oklahoma on May 20.
The deadliest tornado in U.S. history, the Tri-State Tornado of March 18, 1925, ravaged 219 continuous miles of Missouri, Illinois and Indiana. Nearly 700 people lost their lives in that single tornado, according to NOAA. However the twister was not officially classified by NOAA as an EF5 -- the most damaging type -- because of a lack of data, nor were there official records of wind speeds.
On May 22, 2011, the deadliest tornado yet recorded by the new Enhanced Fulita Scale struck Joplin and killed 158 Americans, making it the seventh deadliest in U.S. history. Winds exceeded 200 miles per hour as the EF5 tornado demolished a path that was 22.1 miles long and up to 1 mile wide.
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The second deadliest tornado in U.S. history whipped along the Mississippi River on May 2, 1840, ending 317 lives, according to NOAA’s Storm Prediction Center. The tornado killed hundreds on boats and barges on the river until striking Natchez, where the storm killed dozens more. Like all tornadoes from before 1950, NOAA lacks sufficient data to classify the Natchez tornado as F5 or EF5.
St. Louis, Mo.
St. Louis suffered a tornado’s wrath on May 27, 1896, when at least 255 people died. A study published in Weather and Forecasting estimated that the tornado cost $2.2-$2.9 billion in 1997 dollars when adjusted for inflation and wealth increases, making it the costliest tornado in American history. The death toll made it the third deadliest.
On April 5, 1936, the fourth deadliest tornado in U.S. history struck Tupelo, Miss., and killed 216. A total of 436 people died in the outbreak of 17 tornadoes that included the Tupelo twister. Tetsuya Fujita of the University of Chicago and Tom Grazulis, head of the Tornado Project, retroactively rated the Tupelo tornado as an F5 on the scale invented by Fujita.
The same storm system that lashed Mississippi in 1936 continued on to Georgia where it unleashed the fifth deadliest tornado in U.S. history and killed 203 people in Gainesville. Fujita and Grazulis rated this tornado an F4, meaning winds reached 207-260 miles per hour.
Oklahoma is no stranger to tornadoes. The sixth deadliest on record struck on April 9, 1947. The storm nearly destroyed the towns of Higgins and Glazier. In Woodward, Okla., 100 city blocks were destroyed and 107 lives lost, according to the Tornado Project. A total of 181 people died in the tornado.
The largest outbreak of F5 super-tornadoes occurred April 3-4, 1974. Seven F5 tornadoes struck in a single 24-hour period. In total, 147 tornadoes whirled through the central portion of the United States on that day.
On May 22, 2004, the largest tornado ever recorded hit Hallum, Neb. The twister stretched nearly 2 1/2 miles across. No one died in the massive twister.
Groups of tornadoes or outbreaks can cause as much or more damage than a single giant storm. The “Dixie Outbreak” of April 27, 2011, killed 316 people according to NOAA’s Storm Prediction Center. More Americans died in tornadoes that day than any other in this century.
An outbreak of severe weather battered parts of the midwestern and southern United States yesterday (Feb. 20) with damaging winds and strong storms, including several tornadoes reported in Illinois and Georgia. The same system is working its way over the East Coast today (Feb. 21), with several tornado warnings and watches issued already.
But it's February, not April, when tornado season usually gears up, so what gives?
While the main tornado season typically stretches from spring to early summer, wintertime twisters are not altogether uncommon, said Greg Carbin, a meteorologist with the National Weather Service's Storm Prediction Center in Norman, Okla.
"Tornadoes can happen at any time of the year, in any month of the year, and in just about any location in the country," Carbin told Live Science.
Yesterday's tornadoes in the Midwest struck during the so-called transition season — the period between winter and spring.
"Typically we see these tornado events in the transition season, and the reason for that is you have the vestiges of both seasons that can bring about the ingredients for strong, violent storms," Carbin explained.
In the winter and early spring, tornadoes are often associated with the jet stream, which is a band of strong winds high above the atmosphere that can influence weather patterns by jostling air masses around.
Tornadoes form in environments of unstable air, usually when warm, moist air is trapped under a layer of colder, dryer air. In Illinois, unseasonably warm, springlike temperatures mixed with cold air to produce stormy conditions, said Illinois state climatologist Jim Angel.
"We had a cold front that moved through the state, and at the head of it, we had warm moisture coming up from the Gulf of Mexico," Angel told Live Science. "The warm, humid conditions and the strong cold front pushing through triggered lines of thunderstorms."
Four possible tornadoes touched down in central Illinois yesterday, causing power outages and minor damage in the region, according to the NWS. Severe storms also ripped through Indiana, Kentucky, Alabama, Mississippi, Tennessee and the Carolinas, and several tornadoes were reported in Georgia.
Today, Angel and his colleagues are conducting surveys in the aftermath of the storms, but so far no casualties have been reported. Once the scientists parse the data, Angel will also be able to say precisely how many twisters touched down in the state.
Still, tornadoes in February are not necessarily harbingers of the main tornado season to come.
"There's no real connection that we've been able to find," Carbin said. "And, up until yesterday, we were running at a record low number of tornadoes for the year."
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