2013 Expected To Be Near-Normal Year For Severe Weather
March 10, 2013
By Wally Kennedy, The Joplin Globe, Mo.
JOPLIN, Mo. -- This year is shaping up to be a near-normal year for severe weather, the experts say.
It is not expected to be like 2011, which was a severe year for tornado outbreaks with more than 1,700 nationwide. Joplin, Mo., and several Southern states were hit hard.
And it should not be like last year, either. Last year was one of the least-active years for tornadoes in the past 58 years, according to the National Weather Service. There were 1,072 tornadoes in 2012.
The difference between 2011 and 2012 underscores the difficulty forecasters face in getting a sense of how severe conditions could be in April and May, when the probability of tornadoes is at its highest.
"It shows how variable the atmosphere can be. You can`t ask for a better example of that than the last two years, said Greg Carbin, a severe-weather meteorologist with the Storm Prediction Center in Norman, Okla.
In 2011, there were 939 tornadoes that were EF-1s or greater on the Enhanced Fujita Scale, which measures the severity of tornadoes based on damage. Last year, there were 380 that were EF-1s or greater.
"2011 was one of the worst years ever. Last year was the fourth lowest in the last 58 years for EF-1s and greater, Carbin said. "It was quite a reversal.
Carbin said improved climate modeling is helping forecasters "latch onto something real 10 to 12 days out before severe weather occurs. In the past, forecasters at best could see a week into the future.
"Climate models are getting better at depicting larger-scale interconnections between the oceans and the atmosphere, he said." We can use this capability in our models now that are 10 to 12 days out. We can see a pattern setting up for decent storm systems.
Weather forecasters believe that the temperature of the water in the equatorial region of the Pacific Ocean (The El-Nino/Southern Oscillation) and the Gulf of Mexico are keys to predicting whether severe weather will be more frequent from one year to the next.
La Nina is a cooling of the surface water of the eastern and central Pacific Ocean. It occurs somewhat less frequently than El Nino, which is a warming of those same waters.
When the La Nina was in effect in early February, the temperature of the Gulf was well above normal; with the fading of La Nina, it has moved back to near normal.
New research, triggered by the violent tornadoes that struck Tuscaloosa, Ala., and Joplin, Mo., in 2011, is showing that the La Nina/El Nino climate pattern might now portend outbreaks of severe weather in the lower 48 states.
The research, led by Sang-Ki Lee, with the University of Miami and the National Oceanic and Atmospheric Administration, focused on "trans-Nino," an ocean configuration that occurs during the transition phase as an El Nino or a La Nina begins or ends.
A trans-Nino has lower-than-average surface temperatures in the central tropical Pacific and higher-than-average surface temperatures in the eastern tropical Pacific. That alignment was present in seven of the 10 highest tornado outbreak years from 1950 to 2010. That configuration also occurred in 2011.
Lee said the trans-Nino feature is not occurring at this time.
"This spring, the tropical Pacific will be slightly colder than average."
NOAA`s seasonal forecast suggests that will continue through this spring, he said in an email to The Globe.
The most tornadoes to occur in one year was 1,817 in 2004.
Last year, there were 1,072 tornadoes.
In 2011, there were 1,700 tornadoes.
The annual average for the past 10 years is 1,300.
(c)2013 The Joplin Globe, Joplin, Mo.
Story Image: A large flag hangs from a cane beyond a pile of debris in a devastated neighborhood in Joplin, Mo., on May 28, 2011. (Charlie Riedel, AP)
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