Mississippi is still reeling from the deadly tornado that struck and killed at least 25 people on March 24.
The violent storm was particularly destructive to the small town of Rolling Fork and neighboring areasleaving in their wake vandalized buildings and demolished vehicles.
The tornado formed from a supercell thunderstorm, the least common type of thunderstorm, but one capable of producing severe weather, including violent tornadoes.
Storm forecast officials had issued warnings for the storm for several days. The first tornado warning was issued just before 8 p.m. Central Time on March 24. As the tornado began to approach Rolling Fork, the National Weather Service (NWS) issued an extremely rare tornado emergency, warning of a life-threatening situation.
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The warnings were issued 11 minutes before the tornado hit the small town.
While that doesn’t sound like a long time, it’s the standard range for predicting a tornado.
Meteorologists can predict storms capable of producing tornadoes in advance, and weather forecasting systems are the most advanced ever.
But tornadoes can form in just a few minutes, and it remains extremely difficult to predict when and where they will occur.
So why are these destructive systems so difficult to predict, even with advanced weather forecasting systems?
Dr. Jana Houser, an associate professor of meteorology at The Ohio State University and an atmospheric scientist specializing in the study of supercells and tornadoes, said news week that there are essentially two levels to forecasting tornadoes.
“The first level, if you will, is when we’re investigating environments that are potentially favorable for tornadoes. We’re actually pretty good at this! We’ve learned, over the last few decades, what environmental parameter space is required for the most tornadoes develop. shape,” Houser said. “This allows us to identify and characterize environments several days in the future where tornadoes could be possible. The second level is a bit more complicated.”
This is when storms start to form and scientists start trying to determine whether or not a tornado is going to happen.
“Scientists don’t yet understand all the nuances of figuring this out and differentiating between storms that occur in essentially the same exact environment, but one produces a tornado and another neighboring storm doesn’t, even when they’re separated by distances that are relatively small,” Houser said. . “So the part of looking at a storm and figuring out if it’s going to produce a tornado in the next 15 minutes is really challenging.”
A 2010 study published in the Journal of the American Meteorological Societyand found that, over a five-year period, about 26 percent of all tornadoes that occurred in the US were not warned by the NWS.
However, most of these unrecognized tornadoes were weak. The study also found that 11 percent of all tornadoes that caused fatalities occurred from unwarned tornadoes.
There are also many false alarms with tornadoes.
“What operational meteorologists do is take environmental conditions into account while looking for signals in ongoing storms, primarily using radar data,” Houser said. “If they see rotation start to develop in a storm, and that storm is in an environment that is particularly favorable for tornado formation, they will often issue a warning. The challenge is that we don’t know with a lot of confidence if that storm is in “It will actually produce a tornado. That’s why you end up with a lot of false alarms. A lot of storms that are warned don’t actually end up producing tornadoes.”
In many cases, the predictions have been accurate and correct. An example is the tornado that struck western Kentucky on December 10, 2021. The tornado caused at least 57 deaths.
In this case, forecasters predicted that the tornado would hit Mayfield, one of the cities most badly damaged by the tornado, at 9:30 p.m. This is exactly the time the tornado ended up hitting.
This shows the great improvement of technology in recent years.
Before the emergence of certain forecasting technologies in the late 1980s, federal data showed that scientists could issue warnings for just over half of the 88 severe tornadoes, as reported by the New York Times. Today, 97 percent of the time, tornado warnings are issued before they arrive.
But unfortunately, the warnings do not prevent them from being deadly.
How dangerous are tornadoes?
As sadly seen in Mississippi, tornadoes can be deadly. According to data from the NWS, in an average year there are 80 deaths and 1,500 injuries from tornadoes in the US.
With the Mississippi case, it turned out that the conditions were perfect for the tornado to last a long time, allowing it to cause more destruction.
“Conditions were perfect for a storm to last a long time, and that’s not often the case,” Lance Perrilloux, an NWS meteorologist in Jackson, Mississippi, told the newspaper. BBC. “It caused the tornado to wreak havoc over a long distance.”
Although this particular tornado was more destructive than most, any tornado is a hazard.
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“Tornadoes are so dangerous because the wind speed inside them can be incredibly high. The fastest observed winds in the world have been associated with tornadoes,” Houser said. “The average tornado has wind speeds on the order of 100 to 120 mph. The most violent and strong tornadoes can have winds in excess of 300 mph.”
Later, when the speed of the wind hits the structures, it causes them to tear. The winds then cause the debris to fly through the air.
“That debris creates an additional threat to other buildings around you because then you have projectile objects hitting buildings, stores, bridges, etc.,” Houser said. “In fact, the majority of deaths that occur associated with tornadoes are the result of blunt force trauma to the head associated with flying debris.”
How are tornadoes formed?
Any type of severe thunderstorm has the potential to produce a tornado, but most form from a supercell thunderstorm. However, these storms are quite rare.
Supercell thunderstorms are violent storms that last for a long time, circling from above. In these storms, the aloft circulation builds upward through the storm, and then downward toward the ground as well.
Most supercell thunderstorms cause violent weather, but only about 30 percent actually result in tornadoes, the NWS reported.
“Tornadoes form in a rather complicated way. Tornado formation requires moderately strong rotation to be present on the ground before the tornado itself forms. The source of this rotation is not entirely clear, nor is it necessarily the same for each tornado. Houser said.
“But we think that, most of the time, it gets there from the front (or northeast) part of the storm, where downward-moving rain and cold air meet the warmer, more buoyant air in the environment. This boundary creates a horizontal spin like a bicycle tire, and that spin is carried out the rear of the storm, where it meets a zone of downward-moving air called the trailing flank downdraft.
“That downward-moving air now pushes this spinning air toward the ground and simultaneously acts to reorient it from spinning like a bicycle tire to spinning like a top. When this area of rotation is located below the strong upward-moving air, “Towards the storm’s updraft, the spin concentrates and stretches upward in a manner consistent with an ice skater pulling their arms. The spin then rapidly intensifies and moves upward over time forming a tornado.” .
Why are there so many tornadoes in the United States?
Tornadoes occur in many countries around the world.
However, they are more common in the US On average, the US receives 1,200 tornadoes per year. Why is this?
“The reason they are so prolific here and not elsewhere has to do primarily with the geography of the US. The environmental ingredients needed to form a tornado include, warm, moist surface, air, cold air over that surface warm, some kind of an atmospheric feature to get air, move up, and a strong change in wind speed and direction with height. The central and southern US is perfectly positioned for this combination of conditions.
“The Gulf of Mexico, for example, provides a source of moisture. And the Rocky Mountains act as a natural wall that inhibits jet streams.
“This works to carry warm, moist air northward across the central plains and the southern part of the United States. Also, we often have cold air in the air that promises the south with the jet stream pattern a large scale,” Houser said.
“This occurs in what we call atmospheric troughs. Troughs are home to both cold air and strong winds. Because we have the relatively cool large landmass of Canada to the north, all the ingredients can really come together in the center. and southeastern United States”
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