Tornadoes in the Southeast are getting worse -- and they're often the deadliest

This region includes portions of eastern Texas, Louisiana, Arkansas, Tennessee, Mississippi, Alabama and Georgia. Tornado Alley includes the area from central Texas stretching north to Iowa, and from central Kansas and Nebraska east to western Ohio, according to the National Oceanic and Atmospheric Administration.

While Tornado Alley in the Great Plains still leads in the number of tornadoes, more are appearing in the South. And tornadoes shifting to this region can take a devastating toll.

Dixie Alley tornadoes are harder to spot and often occur at night

Unlike the Plains, where a tornado can be seen coming from miles away, the South has more rugged terrain and more trees, making it more difficult to spot a tornado. Many tornadoes that occur in this area are "rain-wrapped," so they are less visible to the naked eye, CNN meteorologists say.

More heavily forested areas in the South leads to more trees being toppled by storms or turned into projectiles as well.

Tornadoes in the South tend to stay on the ground longer and move faster. Many storms in Dixie Alley are pushed by a stronger jet stream, which results in faster-moving storms.

It's not uncommon for a tornado in the Southeast to travel faster than 50 mph (80 kph). This puts more pressure on forecasters to get a tornado warning out in enough time for the public to react, CNN meteorologists say. Nashville residents had only minutes of lead time ahead of the deadly tornado that struck there Tuesday just after midnight.

Many of the storms occur overnight, when most people are sleeping and unaware that a tornado is approaching. Many homes in the Southeast lack a basement or underground shelter. In 2008, the US Census Bureau reported that only 10% of new homes included a basement whereas 75% of new homes in the Northeast and Midwest had a basement.

Parts of the Southeast are more densely populated, which means more deaths

It's not an anomaly that tornadoes appear in the Southeast every year, but they present different vulnerabilities, Victor Gensini, a professor of meteorology at Northern Illinois University, told CNN last year.

"As you move east from Kansas to Mississippi, Georgia, Tennessee, the population density increases rapidly and we also have an issue in the Southeast of more mobile homes," he said. "If you get hit in a mobile home from a tornado, you're much more likely to be killed. You just have a really unique exposure and vulnerability problem."

Gensini was co-author on a study that started tracking tornadoes in 1979 and they observed a shift towards the Southeast around 2008.

Even though there are fewer tornadoes in Dixie Alley than in Tornado Alley, there have been more deaths in the Mid-South/Southeast region. That's because now they're occurring in more populated areas.

The average tornado fatalities were highest in Alabama with 14 deaths per year followed by Missouri, eight, and Tennessee with six deaths per year, according to the National Weather Service data from 1985 to 2014.

Although those states led in the average number of tornado fatalities, they were not the states with the most tornadoes. The highest annual average number of tornadoes were reported in Texas with 140, Kansas with 80, and Florida with 59, according to the weather service. Meanwhile, Alabama averaged about 42 tornadoes per year.