A swarm of tornadoes that tore through the Midwest and Southeast in early March has earned the grim title of the nation's first billion-dollar weather disaster of 2012.

From March 2 through the early hours of March 3, 132 tornadoes were reported across nine states. Although those numbers are preliminary, and will undoubtedly decrease once overlapping reports are eliminated, their aftermath was devastating, causing more than $1.5 billion in damage and killing 40 people.

The storms killed four people in Ohio, but they took the greatest toll in Indiana, killing 13, and Kentucky, where 23 people died.

The costly disaster follows on the heels of a record-breaking year for devastation wrought by the vagaries of the weather and longer-term climate conditions. Last year, the United States experienced 14 separate events that caused $1 billion or more in damage. Five of those events were tornado outbreaks.

Adding it up
Last year's costliest weather disaster was the late April 2011 tornado outbreak, which produced an estimated 343 tornadoes across Midwestern and southern states, killing 321 people and causing some $10.2 billion in damage. [The Top 5 Deadliest Tornado Years in U.S. History]

This year's early March tornado outbreak was significant for a number of reasons, according to Jake Crouch, a climatologist with the National Climatic Data Center (NCDC), and co-author of a new State of the Climate report from the National Oceanic and Atmospheric Administration released today (April 9).

Atmospheric conditions that made for unseasonably warm temperatures in late February and early March across huge swaths of the United States allowed warm, moist air up to areas where it could collide with cold, drier air, Crouch said, a key ingredient for severe weather.

"And when we get a storm system moving through, interacting with high temperatures and moisture, it creates instability in the atmosphere and that favors these large outbreaks," Crouch told OurAmazingPlanet.

He said the timing was unusual, though. "We don't expect to have large tornado outbreaks with high human loss this early in the season," Crouch said.

Overall, the preliminary count for March tornadoes is 223. Once numbers are confirmed, the month could be the most active March ever recorded, according to the NCDC report.

Putting it in context
However, Greg Carbin, warning coordination meteorologist at NOAA's Storm Prediction Center, cautions that numbers alone don't tell the full story.

"If you look at the history of significant tornado activity, there are a large number of outbreaks that occur in March and April," Carbin told OurAmazingPlanet.

And they have claimed many lives before, he said. March tornado outbreaks killed 40 people in 1994, 64 people in 1984, 58 people in 1966 and 209 people in 1952.

In addition, Carbin said, because of population increases and better technology, researchers have gotten a lot better at seeing tornadoes, so weaker twisters that would have escaped a count 50 years ago can make for higher tornado numbers.

Carbin did say the early March outbreak was indeed a dramatic event. However, he said that it's difficult to qualify just how dramatic, given that tornadoes are, by their very nature, what Carbin calls "atypical events."

"When people talk about what's normal for tornado activity, well, there really isn't a "normal" for tornado activity because it is an atypical atmospheric event," he said. "That makes it very difficult to quantify what normal is."

Outlook for 2012
However, Carbin did say that temperature is something that can be tracked over a long period of time, and thus it is possible to confidently say what normal is — and both he and Crouch said that March 2012 was a huge outlier.

"It blew the doors off any existing records," Carbin said. "I think everybody is quite shocked at how warm a month March was across the continental U.S."

Crouch said that the mild winter and lack of snow in much of the eastern U.S. makes the flood outlook for 2012 far less ominous than last year, when floods caused billions of dollars in damage and accounted for two of 2011's billion-dollar disasters.

However, dry conditions might have some troubling consequences in other parts of the United States, Crouch said.

A record drought set the stage for devastating wildfires in Texas in 2011, and caused more than $750 million in damage.

"And this year, the dryness is a little farther west, in California, Nevada and Arizona," Crouch said.

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