The tornadoes that ripped through the Midwest and South over the weekend killed about two dozen people, officials said Monday, making 2008 the deadliest year so far for twisters in a decade.
According to the National Weather Service, 96 people have lost their lives in a year that has seen an unusual number of storms. In 1998, 115 had perished by May 11.
"It's certainly one of the biggest years we've had," said Harold Brooks, a meteorologist at the National Severe Storms Laboratory in Norman, Okla.
One reason, he said, was a turbulent winter in the northern half of the country. When cooler low-pressure systems from the north collide with warm air from the Gulf of Mexico, it creates extreme weather conditions that can spawn a tornado.
"We've had a lot more times when the atmosphere is primed for tornadoes to occur," Brooks said.
What is unusual about this year is the large number of storms in January and February -- clustered in places that are normally too far north for winter twisters, such as Illinois and Wisconsin -- said Greg Forbes, a severe-weather expert at the Weather Channel.
On Jan. 7, for example, two strong tornadoes tore through southern Wisconsin. There has been only one other January tornado in that region since 1844, Forbes said.
February saw an onslaught of twisters that killed more than 50 people in Arkansas, Tennessee, Kentucky and Alabama.
"What we're seeing over the last 10 years is more wintertime events and [storms] creeping north," Forbes said. "Whether that's global warming or not, you can only speculate."
Forbes, who keeps his own list of confirmed tornadoes, said there have been 654 so far this year. The chart-topper was 1999, when 676 tornadoes were recorded in the U.S. through May 11. Though there is a lag of several months in the official tally, "we continue to be on a record pace," Forbes said.
Last weekend's storms devastated rural stretches of northeastern Oklahoma and southwestern Missouri. Tornadoes also touched down in Georgia, leaving 18,000 without power.
Half of the dying mining town of Picher, Okla., which is already a federal Superfund cleanup site, was flattened.
The federal government is in the process of buying out the town's residents, but only about half the homes had been assessed by the time the storms hit Saturday night, killing seven. Few residents in the impoverished area had insurance, and they fear they will be left with nothing. Oklahoma and federal officials vowed Monday to find a way to continue with the assessments.
That is little comfort, said Ed Keheley, a rancher who has spearheaded the fight to compensate homeowners in Picher.
"It still has not sunk into people that they have no place to go back to," Keheley said. Of the town, he added, "It's done. It's toast."
In Missouri, emergency workers were slowly restoring electricity to more than 7,000 people after the storms cut a 12-mile-wide swath along the Oklahoma border.
The twisters killed 17 people in Missouri, injured 88 and destroyed more than 100 buildings.
One family of four was killed driving to a wedding.
"It wasn't real pretty," said Mac McKeough, a spokesman for the Office of Emergency Management in Newton County, Mo.
This year's high death toll may result from the fact that many of the storms have hit at night, said Kishor Mehta, an expert on tornado damage prevention at Texas Tech University in Lubbock. Residents have a harder time spotting twisters in the dark and may not get warnings in time.
He said the year's devastation highlights the need for residents of tornado-prone regions to build shelters in their homes. It is also a reminder of how changing population patterns may make people more vulnerable. "As we continue to sprawl, we are exposing a larger number of people to the hazards of tornadoes," Mehta said.
The deadliest year for tornadoes since the federal government began regular tracking was 1953, when 519 perished.