The month of March is known for its extremely volatile climate, as warm spring conditions struggle to replace the cold of winter. When and where the collision between the two is found, severe weather and tornadoes are likely to occur.
This common March collision is on its way from Tuesday to Thursday in the southern U.S., with a particularly dangerous weather outbreak, probably Wednesday and Wednesday night, from Arkansas to Alabama. There is a threat of numerous tornadoes, with some large and powerful tornadoes possible.
On Wednesday morning, the NOAA Storm Prediction Center issued a “high-risk” warning – 5 out of 5 on the warning scale – saying they are expected to begin this afternoon via “returns long and intense along with harmful winds and big hail. ” parts of Louisiana and Arkansas, moving east to Mississippi and Alabama.
Since 2012. There have been no “high-risk” warnings in March since 2012. This is almost as dangerous as it occurs, with likely widespread, destructive, and life-threatening tornadoes.
For forecasts it is not surprising that the severe spring weather season starts strong. This is because there is still a formidable La Niña event present in the tropical Pacific Ocean, which is usually associated with a more extreme phenomenon, wavy ray current and therefore a greater tornado threat.
In addition, tornadoes are becoming more common in March. This past weekend, like historic snowfall plagued Denver and Cheyenne, el same storm produced 19 tornadoes in the Texas Panhandle. In a 2015 paper, researchers found that the start of the tornado season has increased 13 days since the late 1970s.
And the threat of the tornado not only changes over time, it also changes place. A 2018 study found that there is a declining trend of tornadoes in what is traditionally known as Tornado Alley in plain states, but growing trend of tornadoes occurring throughout the south-middle – the same general area that is expected to face this week’s severe weather outbreak.
The danger may already increase in this region. Two of the deadliest tornado outbreaks in the last two years occurred in early March in the southeast. In 2019, 41 tornadoes concentrated in Alabama and Georgia killed 23 people. In 2020, there were 25 fatalities while 15 tornadoes broke Tennessee.
This week’s threat
The key attributes of this storm are both its cool air pool at the height and the fact that it spins like a peak. The elevated cold air allows warm air to rise to the surface more quickly, creating larger storms. The turning motion of the storm helps to transmit the turning motion to individual storms and any tornadoes they may generate.
Normally, these revolving storms rise northeast of the Mississippi Valley area, but this storm cannot due to an atmospheric block in the north. Instead, it will continue to head east on Wednesday and Thursday, with strong dynamics throughout the southeast, leading to the threat of a widespread outbreak and a particularly dangerous situation.
The main event will occur as the cold turning storm slides eastward, colliding with the warm, humid air coming out of the Gulf of Mexico.
Outside of the “high risk” bullseye, the Storm Prediction Center has highlighted a wide area for severe weather “enhanced risk” (3 out of 5) from the southern tip of Missouri in the southeast to the Florida Panhandle .
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Burial within this wider improved area presents an even greater risk, which is seen in red on the map. Technically, this is called “moderate risk” and is an abnormally large risk area, but the name is misleading. A moderate risk is a 4 out of 5 on the severe weather scale and indicates the potential for very dangerous severe storms. This includes cities such as Little Rock, Memphis, Tupelo and Birmingham.
If you live in any of these risk regions, pay close attention to local warnings and remember that storms will be even more dangerous as night falls and tornadoes become harder to see. Computer models indicate that the threat to large tornadoes will be maximized Wednesday evening and night.
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Night tornadoes are more common in the south-middle. This is because, unlike the states of the drier plains, which rely on the heat of the day to provide energy to storms, the region adjacent to the Gulf of Mexico, due to additional humidity, can maintain an atmosphere. more energetic and unstable much later in the night.
The threat of severe weather will persist until Thursday as the system shifts to Georgia and the Carolinas, where tornadoes, damaging winds, hail and lightning will once again be likely to occur.
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Southeast most vulnerable to tornado damage
There are several reasons why tornadoes are more dangerous and destructive in the southeast, in addition to the greater tendency for them to occur at night. This is the biggest vulnerability trends in stronger severe storms in this region they are worrisome.
Because these storms form in a wetter environment, they tend to wrap up in the rain and be harder to see. Also, unlike plain states, where the terrain is often open, allowing people to spot tornadoes miles away, the southeast is covered with more hills and trees.
The region also has a higher population density and many houses with a weaker setting, which increases the risk of damage and death. Research shows that this danger will continue to grow as construction continues to expand and the distribution of the tornado will change, with a possible triple increase in disaster potential by the end of the century.
While scientists are still trying to figure out why tornado patterns change, there is a lot of research showing dangerous storms and the environments in which they form increase, at least in part because of the human cause. climate change.
A 2016 study showed that since the 1960s, the frequency of tornado outbreaks is increasing and the most extreme of these outbreaks is increasing at the fastest rate. And it is the outbreaks, unlike individual tornadoes, that are usually the most destructive, with 79% of fatalities from 1972 to 2010 occurring in outbreaks.
Probably the most revealing paper on tornado trends was published in 2018 by Dr. Victor Gensini and Dr. Harold Brooks. His research shows a clear upward trend in tornadoes in the mid-southern and lower Mississippi Valley, an area that, as mentioned above, is particularly vulnerable. He greater increase is near cities like Little Rock, Arkansas; Memphis, Tennessee; Tupelo, Mississippi and Tuscaloosa, Alabama. This coincides with the biggest threat zone on Wednesday.
CBS News spoke with Gensini, an extreme climate researcher at Northern Illinois University (NIU). According to his research, in the south-middle zone, a local area the size of a city can be expected to experience an average of 4 additional tornadoes per decade just 40 years ago.
In the image below, taken from Gensini’s paper and adapted by NIU, the red shaded area indicates where tornadoes are rising, almost precisely the zero point of this Wednesday’s planned outbreak.
Gensini, Brooks 2018
In the blue shadow zone, the number of tornadoes is declining in Texas and the lowlands. Although this area, commonly known as Tornado Alley, still has the highest density of tornadoes, the growing trend is weighing toward its east.
While Gensini can’t say for sure why the trend is eastward, he says yes. consistent with what we would expect from climate change. This is because as the climate warms, the desert and dry regions of the southwest are expanding eastward. This limits the instability on the states of the plain and therefore also the formation of tornadoes, and pushes the area of convergence between dry and humid air to the east.
In addition, the waters of the Gulf of Mexico and adjacent land areas are warming due to man-made climate change. This entry of more heat and moisture provides more energy to feed more extreme tornado outbreaks in the southeast.
And while humans continue to warm the climate, most sciences agree that the environment that creates these dangerous tornadoes will continue to be more unstable and dangerous.