The tornado hot spots and what we’ve learned since April 27


LIMESTONE COUNTY, Ala. – It’s more than a feeling of déjà vu. History is repeating itself, especially when it comes to the weather.

It’s obvious, just on the surface of the story of Alabama with tornadoes. Research has proven Alabama to be one of the most tornado-prone areas of the country, but there are places in our state where that seems to be an understatement.

Take the example of Tanner.

The Alabama tornado database dates back only to 1950.

During this period of seven decades, 41 tornadoes have occurred within 10 miles of Tanner, according to Storm Prediction Center data.

In exactly the same amount of time, only 23 tornadoes have landed within 10 miles of Lester in the northwestern part of the county.

This is obviously no accident; there is something more to it.

Is it the Tennessee River?

You can often hear “this is the river” when the tornado story returns here. It’s one thing to say it, but it’s another thing to prove that there is a cause beyond bad luck.

Enter UAH research meteorologist Dr Tim Coleman.

“I think there is a combination of the two,” he says. “You would need to prove it with absolute certainty. You would need hundreds of years of tornado data, but we know there are stationary physical processes. They are related to things like mountains, friction, different types of land cover, and heat. “

“Things like that are stationary. We see some theories and tornado maximums, at least some of them, fit the theory. So we can explain some of the tornado minimums and maximums, but others we look at them and say we really don’t know what’s going on here.

Dr Coleman says we have some understand why communities like Tanner so often seem right on target; we just don’t know everything yet.

“In Southern Limestone County, the air blows over the Tennessee River, so it accelerates due to the least friction,” he said. “Then when it comes into the county it goes over land and starts going through the urban areas around Athens and west of Huntsville near County Line Road, so it starts to slow down. This creates a convergence of the air and can sometimes trigger a tornado. “

Changes in surface roughness from land to smooth river can improve shear, but that’s not the only reason southern Limestone County is a tornado “hot spot”.

Friction is resistance, and changes in the ground surface produce friction when air blows over it: influencing the speed and direction of the wind. When the wind speed and direction change over short distances horizontally and vertically, which increases the shear available for a thunderstorm for the development of a tornado: sometimes.

Development model of a tornado in a thunderstorm

How does this help?

UAH researchers are working on this issue day in and day out with the goal of improving tornado warnings.

Dr Coleman says research continues to show promise in identifying reasons why some places are more prone to tornadoes than others, and that will lead to better warnings from the National Weather Service.

The meteorologist issuing a tornado warning will have a better tool for knowing how a storm should behave when moving through a particular environment, which in turn will give more time for true storms producing tornadoes and reduce false alarms. in other cases.

Information like this also helps us at News 19 to deliver urgent and local information when a tornado occurs.

Dr. Coleman’s work goes beyond identifying the problems here and now; he is also working on a new forecast index to better predict storms that produce tornadoes,

“I’m working on something called ‘SHAPE’, which is kind of like instability, but which is created by wind shear,” he says. “Sometimes in the winter we have these events where there’s almost no instability, but we still have tornadic lines of storms, so I’m working on a parameter to help predict them. We don’t stop. We are always on the lookout for new things. “

How worried should you be if you are near a “hot spot”?

We know from living in the state that Alabama, in general, is a “hot spot” for tornadoes. Dr. Coleman’s research shows that none of us are “safe,” but that doesn’t necessarily mean we have to live in fear.

“Any place still has a one in 200 chance, and that’s in the most risky areas of Alabama, about a one in 200 chance of actually being hit by a tornado,” he said. . “On April 27, 2011, approximately 1.1% of Alabama’s land cover was affected. Now that’s a lot, but that means you had a 98.9% chance of NOT getting hit by a tornado that day. “

In April 2014, Dr Coleman and Dr Grady Dixon defined a new ‘tornado alley’ in the south: Dixie Alley.

An area near Jackson, Mississippi, northeast to near Decatur, Alabama, had the highest concentration of strong to severe tornadoes in the country between 1973 and 2011.

Coleman & Dixon: average annual path length of all significant passages (F-2 to F-5) within 40 km of a point between 1973 and 2011.

The heart of this area is near Dr. Coleman’s property on the Walker-Jefferson County line in central Alabama. An unpublished figure from the newspaper An objective analysis of the tornado risk in the United States surprised Coleman, but that doesn’t scare him.

He’s discovered that the highest probability of an Alabama tornado is right at his home on the Warrior River, but Coleman says he doesn’t live in fear, and neither should you.

“People think they are safe on a mountain side or in a valley,” he said. “None of this is true. You should never be a rider about this even if you live in a tornado minimum. But if you live in a maximum, you don’t have to panic either!

Arm yourself with knowledge and prepare with a plan. This is how you can avoid panic.

NOAA Weather Radio is the best and proven way to make sure you receive a warning when extreme weather conditions are approaching.

You can also receive up-to-date location-based alerts wherever you are on Live Alert 19: available on both ios and Android devices.

It’s what you do with the information that matters. Your tornado safety plan should be simple but flexible. It needs to be flexible because we don’t always have fifteen minutes of turnaround time, sometimes less than five minutes.

Being prepared and informed is the key to weather management.

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