Search For Survivors Begins as Tornadoes Pummel States

By Climate Central

Hours after one of the biggest storm outbreaks in March’s history, residents across at least 10 states turned to the frantic search for survivors on Saturday after a series of tornadoes and severe thunderstorms ripped apart the South and Midwest, killing at least 37.

At last report, the storms killed 19 in Kentucky, 14 in Indiana, three in Ohio and one in Alabama, but the death toll may rise as the scale of the devastation made it impossible to immediately assess the damage.

According to Mike Hudson of the National Weather Service’s office in Kansas City, the breadth of the storm system stretched from the Gulf Coast to the Great Lakes and was so wide that an estimated 34 million people were at risk from severe weather. At one point, the storms were coming so fast that as many as four million people were within 25 miles of a tornado.

Residents comfort each other after tornadoes hit Limestone County in Alabama. Credit: Jeronimo Nisa/Decatur Daily.

In all, the National Weather Service issued 255 tornado warnings on Friday and it received 97 reports of tornadoes from across the central and southern U.S. Just three days into March, and already this month is deadliest March for tornadoes in nearly 20 years. 

Friday's severe weather was set off by a combination of warm, moist air streaming northward from an unusually warm Gulf of Mexico, and cold, dry air moving southeast from Canada. This clash of air masses occurred in conjunction with an extraordinarily strong jet stream, with winds in the mid to upper atmosphere clocked at 150 miles per hour. While the upper level winds were screaming out of the west, closer to the ground, the winds were from the southeast. This difference in wind speed and direction with height is known as wind shear, and it provides the storms with the ability to rotate, spawning multiple tornadoes.

Climate change is already changing the environment in which severe thunderstorms and their associated tornadoes form, and at some point in the future it may have a discernible influence on tornado frequency and/or strength. Tornadoes form when ingredients such as wind shear, warm and unstable air, and a triggering mechanism such as a cold front, come together at the right time and in the right proportions. Massive outbreaks such as this one are rare, and are most common between now and June. The record for the largest March outbreak is 74 tornadoes from March 11-13, 2006.

Radar image of a tornadic thunderstorm hitting West Liberty, Kentucky on March 2, 2012. The image shows a classic “hook echo” pattern typically seen when tornadoes are occurring. Credit: Twitter/Stu Ostro.

In Kentucky, where more than 200 were injured, according to the Associated Press, the National Guard and the State Police searched for an unknown number of missing, and in Indiana, the authorities searched county roads connecting rural communities that officials said “are completely gone.”

Friday’s violent outbreak came just two days after a series of severe storms killed 13 people in the Midwest and South.

As Indiana Gov. Mitch Daniels toured Henryville, a small town of less than 2,000 that was devastated, he called the destruction “heartbreaking.” (CNN posted a dramatic video of the Henryville tornado as it tore across the small town.)

“We're not unfamiliar with mother nature's wrath here in Indiana but this is about as serious as I've seen in the years I've been in this job,” Daniels said.

In Marysville, Ind., most of the several dozen homes that make up the town were destroyed. The town was described as “completely gone.”

“We knew this was coming. We were watching the weather like everyone else,” said County Sheriff Danny Rodden said. “This was the worst-case scenario. There is no way you can prepare for something like this.”

With regards to climate change and tornadoes, no discernible trend has been detected in the long-term observational data, and studies of how tornadoes will fare in a warmer world show somewhat conflicting results, largely because computer models don’t yet have the ability to accurately simulate events on such small scales.

Rrotation track map that shows where strong, rotating thunderstorms tracked on March 2, 2012. Credit: NOAA.

While hurricanes can be hundreds of miles wide, tornadoes are often less than a mile in diameter, which requires much more computing power in order to accurately simulate. Scientists are currently working to overcome that challenge.

Rather than simulating tornadoes themselves, scientists have made progress in studying the factors that make conditions favorable for severe thunderstorms to form.

As temperatures warm, air holds more water vapor, which adds “fuel” to the fire, so to speak. Last spring, when the Southeast was struck by multiple deadly outbreaks, the Gulf of Mexico was warmer than average, and the same situation is occurring today. This is important because it means there is more moisture flowing northward from the Gulf, and a humid environment is necessary for severe thunderstorms to form.

But wind shear, which was present in abundance during this latest outbreak, is projected to decrease as the climate warms. This would suggest that tornadoes will become less frequent in the future.

Which factor wins out in the end - the increase in water vapor and heat energy, or the decrease in wind shear - may determine how tornadoes fare in a warming world.

(Reports from The Associated Press, New York Times, USA Today and The Guardian were used)