Is Nashville Tornado Part Of A Long Term Trend? And Other Thoughts On Tennessee

A neighborhood leveled by the tornado in Tennessee this week. Photo by
Mark Humphrey/AP

They continue to pick up the pieces in central Tennessee after Tuesday morning's tornado or tornadoes that killed at least 25 people and caused destruction extending for dozens of miles.

This disaster has people wondering: Is this part of a trend?

The news is disconcerting. According to CNN:

"In recent years, scientists have noticed an increased frequency of tornadoes in the Southeast, carving a deadly path in what's called Dixie Alley.

The region includes portions of eastern Texas, Louisiana, Arkansas, Tennessee,Mississippi, Alabama and Georgia"

While the more traditional Tornado Alley in the Great Plains and parts of the Midwest still  have more tornadoes than the South, the numbers in the South seem to be growing.

Climate change might be a factor.  

Writing for CBS News back in October, 2018, Jeff Berardelli said storm systems are tending to push dry Southwestern desert air into the Southeast further east and more often. Meanwhile,  there is a tendency for more robust pushes of warm, humid, moist and unstable air moving northward from the Gulf of Mexico.

The leading edge of these impulses of arid air from the west are known as dry lines.  Supercell thunderstorms, which can produce tornadoes, tend to form in the humid air just ahead of the dry line. 

Dry air is less dense than wet air, so it rises more easily.  The dry air that's wanting to rise smashes into the wet air.  The rising air entrains some of that moisture, and you get those thunderstorms.

The tornado peeled apart this stop sign
in Nashville. 

You don't even need an official dry line to get these storms going.  If some dry air moves in from the west into humid air, supercell storms can easily develop in the conditions are right.  That's why these intrusions of dry air into the Southeast can be so problematic.

Now, we can't say Tuesday's Tennessee's tornadoes were "caused" by climate change and the associated rejiggering of dances between different pieces of the atmosphere. After all, deadly tornadoes have always occured in the Southeast.  

For instance, a tornado outbreak in the Southeast in March, 1875 killed 96 people. Another tornado outbreak in 1884 killed scores of people in Alabama.   Tuesday's tornado was the third major tornado to slice through Nashville. The others were in 1933 and 1998.

So all we can say is Tuesday's tornadoes in and around Nashville were consistent with the trend scientists have been seeing.

Southeastern tornadoes are often deadlier for numerous reasons, most of which were present in the Nashville tornado.  Southeast tornadoes are a little more likely to occur early in the season, when jet stream winds make a tornado's forward speed go into overdrive.  Which means there's little time for warning.

Also, as CNN points out, Southeast tornadoes are more likely to occur late at night, instead of late afternoon or evening in Tornado Alley. That means people aren't awake to hear warnings. (The Nashville tornado came through a little after 12:30 a.m.)

The Southeast is more densely populated than the Great Plains, so the more occupied houses are likely to be hit in the South. There's a lot more trees that can topple onto homes, and those trees make it harder to see the twister coming.  Plus, Southeastern tornadoes are more likely to be wrapped in rain.  When that happens, they just look like nasty thunderstorms, and not deadly funnel shaped tornadoes.

TRUMP'S EXAGGERATION

The East End United Methodist Church in Nashvillle was
severely damaged. Photo by Mark Humphrey/AP

The following isn't as big a deal, given the loss of life and destruction in Tennessee. But it's still worth mentioning, as accuracy is important.

President Trump always has to make anything he's involved in the biggest and grandest. It makes him feel like he's handling unprecedented stuff with aplomb. That's nothing close to the truth, but whatevs.

Trump tweeted Wednesday that he's going to Tennessee to support tornado victims, which is of course nice. But he had to note the tornado had a "record size and velocity."

No and nope. The Tennessee tornadoes were certainly stronger than most.  There's a five point so called "EF" scale to measure the ferocity of tornadoes.  An EF-5 is the strongest possible.  The strongest Tennesee tornado was an EF-4 and other tornadoes, or other parts of one tornado path were at a high end EF-3, according to preliminary reports.  

Just five percent of tornadoes reported annually in the United States are EF3, EF4 or EF5 level (EF5's are rare and don't even happen every year. So yeah, the Nashville tornado was bad.

But highest winds in the Tennessee tornadoes were an estimated 165 mph or so.  The strongest known winds in a tornado reached about 305 mph in Oklahoma City and its suburbs on May 3, 1999.

The Tennessee tornadoes were probably no more than a half mile wide. Again, that's unusually large for a tornado. But it wasn't close to the record. That mark is held by a 2.6-mile wide tornado in El Reno, Oklahoma on May 31, 2013.

YES, THERE WERE WARNINGS

Some news reports said that the tornadoes "came without warning," which is false. The National Weather Service office in Nashville issued tornado warnings as the storms rapidly approached the metro area, then raced eastward into the suburbs and small towns for a few dozen miles east of Nashville.

The warnings went out about five to 10 minutes before the tornadoes struck.  That's not a lot of time to prepare, but you can at least get yourself to an interior room or basement. Tornado warnings generally don't have much lead time, especially when tornadoes have a fast forward speed, like the Tennessee tornadoes.

However, some people didn't hear warnings.  That's the difference.  NWS/Nashville did a top-notch job with the warnings, but if people didn't hear or see said warnings, they were worthless, at least to the people who didn't get them.

To get warnings, people should have multiple ways to get them.  For instance, some people rely on warnings from their cell phones. Which is a great way to receive warnings. However, in eastern parts of the tornado zone, some cell phones didn't go off, because the tornado had already wrecked cell towers.

However, weather radios, which broadcast tornado warnings immediately, worked just fine.  So people in tornado -prone zones should probably have two simultaneous ways to get warnings. Set up your phone app, but also buy an inexpensive weather radio. Weather radios cost between $25 and $100, depending on how many bells and whistles you want with it.

Don't rely on outdoor storm sirens.  Those are meant to alert people who are outdoors to take shelter. You won't necessarily hear them from inside your house.

Also, know where to go during a tornado warning and know how to do it quickly.  Basements are best. If you don't have one, go to a closet in the center of the house.  Have blankets and pillows ready there to cover yourself up as added protection.  Another good idea is to have bicycle or motorcycle helmets ready in your safe shelter to put on.  You want to protect your head if there's flying debris, so this would help.