The following essay is available for re-publication in The Conversation.
Dozens of people were killed when tornadoes tore through parts of Arkansas, Mississippi, Missouri, Kentucky, Tennessee and Illinois. The Southeast is vulnerable to these disasters year-round, especially at night, because of the conditions that generated this event.
There were factors that came together to cause the outbreak.
A powerful storm system was approaching the central U.S. from the west. The South was enjoying near-record breaking warmth, thanks to warm, moist air flowing north from the Gulf of Mexico, which brought heavy snow and slick conditions to the colder West and northern Midwest.
The 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 Less dense warm air rises up into cooler levels of the atmosphere when warm and cold air mass collide. The warm air can form storms when it cools.
Strong rotating storms can be created when instability and wind shear combine to create an ideal setup.
The air is warm at the surface and cold at higher altitudes. This causes warm air to rise and form clouds that can produce storms.
How intense was this event?
At least 38 tornadoes have been reported in six states, causing widespread power outages and damage. The National Weather Service uses damage indicators from the Enhanced Fujita scale to rate tornadoes. It can take several days to complete a storm assessment.
At least four tornadoes have been confirmed. The wind speeds of the tornadoes are considered to be strong.
Strong straight-line winds can cause as much damage as a tornado. The National Weather Service conducts in-person storm damage surveys to determine if a tornado or straight-line winds caused the reported damage. The hallmark of a tornado is straight-line winds, so investigators will look to see if debris is scattered in one direction.
There was a tornado that traveled over 200 miles across four states. Why is this unusual?
Most tornadoes stay on the ground for a short period of time and travel a short distance. Long-track and very long-track tornadoes are rare. They make up less than 1% of tornadoes in the United States.
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Long-track tornadoes require a specific set of ingredients. These rare tornadoes form from a single supercell storm that can last for hours.
Strong tornadoes stay on the ground longer than weak tornadoes. Their tracks are long in the Southeast, where significant tornadoes in the cool season move quickly, thus covering more ground.
The previous record for a long-track tornado was from 1925, when the F-5 Tri-State Tornado traveled 219 miles through Missouri, Illinois and Indiana. The Quad-State Tornado is expected to break the record. The National Weather Service will determine in the coming days if one tornado stayed on the ground for more than 200 miles or if multiple tornadoes resulted from the same storm. The agency gave a preliminary rating of 3 or more.
The severe storms that produced the tornado outbreak were tracked by the #GoES16 There were more than 30 tornadoes reported in 6 states. Kentucky's governor said it was the most severe tornado event in the state's history.
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December 11, 2021.
There are more nighttime and winter tornadoes in the Southeast.
tornadoes can occur at any time throughout the year, but spring is typically considered tornado season. In the fall and early winter, the Southeast experiences a second peak in tornadic activity.
At any time of the day, tornadoes can happen. In the Southeast, the ingredients for storms are more likely to be nocturnal than in the Great Plains.
There is an abundance of wind shear in the Southeast. They don't rely as much on rising warm, humid air that creates atmospheric instability as they do on daytime heating of the earth's surface.
Predicting a major outbreak several days in advance was accurate. Watches, warnings and information on how to stay safe were issued by the National Weather Service in Norman, Oklahoma.
Nighttime tornadoes can be deadly. People don't receive warning communications when they are sleeping, which leads to more deaths. People are more likely to be in vulnerable housing at night, such as mobile homes, than during the day when they are at work, because spotting storms is more difficult in the dark.
It's important to have multiple reliable methods for receiving warnings at night, since power can go out and cellphone service can go down. Some people who went to shelters were killed when tornadoes hit the building. During less devastating events, timely warnings that allow people to shelter safely in a solid structure tied to a foundation or basement can mean survival.
The Conversation published this article. The original article can be found here.
