Why So Many Twisters This Year?

Usually, the United States sees about 70 tornadoes between January and March. So far this year, we've had more than four times that number. And almost as many people have died from twisters already this year as usually do in a normal year.

So, what's happening?

Dan McCarthy, a warning coordination meteorologist for the Storm Prediction Center in Norman, Okla., tells The Early Show co-anchor Harry Smith that tornadoes so far this year are as violent though no more violent than in the past, "but there are more of them. We may have set a record in March. We've had 228 reports of tornadoes in March. And of course, now, with the number of reports that we've had this week, we're already looking at 450 for the year."

Last year, the U.S. had 54 reported twisters in March, and 43 the year before. What's more, June is always the most active month, with 281 tornadoes last year alone.

"Normally," McCarthy said, "we average about 55 fatalities a year. Don't get me wrong, we'd love to get those down. But the number, at 39 right now (for this year), is a little bit higher than usual."

What's causing the upsurge?

"I think what's happened is we had a very abnormally warm and very dry winter across the south central and southwestern U.S.," he said. "We faced much of the winter with fires, wildfires across this area. And when spring systems finally started to move in from California into these areas, we were able to pull up Gulf (of Mexico) moisture and that brings on the violent storms."

Is the Gulf warmer than usual?

"I think we did not see the cold fronts we've seen the last couple of years move across the Gulf in February and March," he said. "So, I think the skin temperature of the water down in the Gulf is abnormally warm, or as normal as it could be, and that brings dew points up in the air, which helps fuel the thunderstorms."

McCarthy observed that warning systems "have improved. But, you have to keep in mind that the best way to prepare for tornadoes is to be aware of the situation. The Storm Prediction Center puts out outlooks out to three days, and we have been forecasting these outbreaks, these little outbreaks and we've had five already just within the last 30 days. And then the tornado watch also gives advance warning.

"I think what we also need to do is tell people not only to wait for your county to be warned, but listen for warnings for the counties to your west. That'll give you advance preparation."

McCarthy stressed that "there's really no link" between the number of twisters and last year's unusually active and violent hurricane season.

"Tornadoes are such random occurrences that they are day-to-day forecast type of phenomena," he said. "I think what's really going on is just that we've started the year earlier than we have the last three years. We haven't started really until May or June the last three years. And this year, we've just got off to a roaring start."