By Wally Kennedy
Globe Staff Writer
JOPLIN, Mo. —
Joplin’s upgraded storm siren system was tested Tuesday during the statewide tornado drill. It passed with flying colors.
This will be the first storm season in which the revamped system will be ready for activation after approximately $200,000 was spent last summer improving it.
“Everything went well. The new electronic system proved itself,’’ said Keith Stammer, director of emergency management for Joplin and Jasper County.
The new electronics let Stammer “poll’’ each of the system’s 32 sirens before and after they are activated to determine if there are any functional problems.
“What we do is ask them: ‘How are you?’ They tell us if there has been a rotation failure, a battery failure or a communication problem,’’ he said. “If there is a problem, we send out a repair crew.’’
It has become standard procedure for Stammer to poll the sirens before and after severe weather. Last year, the sirens were sounded only one time — Sept. 7 — in connection with stormy weather.
The question for weather experts is: How many times might they be sounded this year? As advanced as weather forecasting and climatology have gotten in recent years, there is still no way to see much further than a few days into the future, according to climatologists. Predicting the frequency of tornadoes is still as elusive as ever, but progress is being made in understanding the conditions that contribute to tornado outbreaks.
This year is shaping up to be a near-normal year for severe weather, the experts say.
‘Quite a reversal’
It is not expected to be like 2011, which was a severe year for tornado outbreaks with more than 1,700 nationwide. Joplin 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 and the Gulf of Mexico are keys to predicting whether severe weather will be more frequent from one year to the next.
Jack Boston, a severe-weather expert with AccuWeather, a for-profit, worldwide weather forecasting service based in State College, Pa., said, “We are predicting a near-normal tornado season. But that’s not what we were thinking at first.
“We have been watching the La Nina in the equatorial Pacific this winter. If it maintained itself, we were prepared to predict a more active severe-weather season. That might not be the case, however. What we are seeing now is that this La Nina is fading and fading fairly quickly.
“Assuming it fades, we could have a severe weather season more like last year’s. If it should go the other way, we would predict a more active season.’’
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.
“With a stronger La Nina pattern, the water in the Gulf of Mexico becomes warmer than normal. That is very important,’’ Boston said. “Humid air masses originate from the Gulf and come into the Plains, where they fuel severe-weather outbreaks.’’
When temperatures are lower than normal around the equator, he said, “they can have a great influence on how much energy is supplied to the jet stream across the northern atmosphere. When the jet stream energy is off to the north, the Gulf can get pretty hot.’’
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 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.
But this does not mean severe weather will not happen this spring in the Midwest. In fact, the AccuWeather forecast indicates that Arkansas, Missouri, Tennessee and Mississippi are among the states that will be ground zero for severe storms this spring.
Boston said that has to do with the drought. Areas north and west of Missouri, such as Iowa and Nebraska, are worse off in terms of the drought. When an area is extremely dry, the humid air from the Gulf is drawn out by the drier soil. That, in turn, lowers the probability of severe weather.
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. AccuWeather is predicting 1,150 tornadoes this year.
Source: National Weather Service, AccuWeather, National Oceanic and Atmospheric Administration