Tornadoes in U.S. at lowest level since at least 1954

1:11 PM, May 13, 2013   |    comments
Storm clouds move over southern Spring Hill and Columbia, Tenn., on March 2, 2012, after it was reported that the storm could spawn a tornado in Spring Hill. / Sanford Myers / File / The Tennessean
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Tennessee is seeing more tornadoes than usual this year, but there have been no deaths linked to twisters so far.

Since the beginning of 2013, the National Weather Service in Nashville has counted 34 tornadoes, with the majority of them, 22, happening on Jan. 30.

"We're trending above average ... and it is an anomalous thing because of that one day," said Trevor Boucher, a meteorologist with the weather service in Nashville. "We've already passed our average for tornadoes for this year."

According to statistics kept by the weather service, Tennessee saw 37 tornadoes in 2012, 80 in 2011 and 36 in 2010.

Boucher pointed out that 2011 was way above average because of a tornado outbreak on April 27.

Tennessee's average yearly tornado count, calculated from 1991 to 2010, is 26, according to Boucher.

"What's problematic for Tennessee is that the majority of the tornadoes we see happen at night," he said. "It's hard for people to see them. If it impacts a forest and nobody's there, then we don't know it happened."

The situation in Tennessee stands in stark contrast to what's happening in the rest of the country.

In the past 12 months, the U.S. has seen the fewest tornadoes since at least 1954, and death tolls from the dangerous storms have dropped dramatically since 2011.

Just two years after a ferocious series of tornado outbreaks killed hundreds, the U.S. so far this year is enjoying one of the calmest years on record for twisters. Through the end of last week, tornadoes had killed only three people in 2013; by the end of May 2011, 543 Americans had died in twisters.

The seven people killed from May 2012 to April 2013 are the fewest in a 12-month period since five people died in the period from September 1899 through August 1900, according to Harold Brooks, research meteorologist at the National Severe Storms Laboratory in Norman, Okla.

The year-to-date count of tornadoes is probably approaching the lowest 10 percent of all years on record, reports Greg Carbin, warning coordination meteorologist with the Storm Prediction Center in Norman.

The reason: an unusually cool weather pattern from the Rockies to the East Coast.

"Generally, the lower the temperature and/or the drier the air, the lower the number of thunderstorms," said AccuWeather meteorologist Alex Sosnowski.

Severe thunderstorms produce tornadoes, along with large hail and high winds.

Quiet May for U.S.

So far in May - usually the nation's most active month for twisters - only three tornadoes have formed. All have been rated EF-0 on the Fujita scale of tornado intensity. EF-0 is the weakest rating, with wind speeds of about 65 to 85 mph.

The EF-5 tornado that ravaged Joplin, Mo., in May 2011 had estimated wind speeds of 250 mph and killed 158 people.

"The extraordinary contrast underscores the crazy fluctuations we've seen in Northern Hemisphere jet stream patterns during the past three years," said Weather Underground meteorologist Jeff Masters. "Call it 'weather whiplash' of the tornado variety."

Current weather patterns are expected to continue into the first part of summer, likely keeping 2013 well behind the curve for violent thunderstorms and tornadoes, AccuWeather reports.

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