Tornado activity deadliest in a decade

Ninety-eight deaths attributed to tornadoes this year have made 2008 the deadliest year so far for tornadoes since 1998 and the seventh deadliest since 1950, according to USA Today. The U.S. experienced 47 killer tornadoes during the past weekend, and continuing at this rate could make 2008 the year with the most tornadoes since 1950.

The Weather Channel reports 47 separate tornadoes as of May 11, which makes a total of 636 for the year so far. The only year to exceed that count is 1999, when 669 tornadoes hit through the same date.

Wind conditions and weather patterns have been ideal for creating tornadoes this year, meteorologists say. The jet stream, a shifting river of air at high altitudes, has been moving from the southwestern U.S. toward the Great Lakes, pulling moist air from the Gulf of Mexico. Tornadoes are spawned by the winds created by warm and cold air.

"We've had a strong contrast in temperatures with cold air from the north, and warm, moist air from the Gulf of Mexico, and with that clash of air masses ... (it) produces tornado outbreaks," says Andrew Orrison, meteorologist for the National Weather Service, Camp Springs, Md.

Generally, tornado season runs from late winter through mid-summer. May is the Southeast’s peak tornado period, and July is the peak period for the upper Midwest and northern Plains states.

Some southern states have been hit hard this year. Mississippi had 49 tornadoes before this past weekend’s storms; Alabama has had 45 tornadoes; and Arkansas has had 49 tornadoes. All have exceeded their annual tornado averages.

Date : 5/16/2008