Tornado Season: What You Need to Know

Photo Courtesy: Steve Piltz/NWS-Tulsa

(TULSA, Okla.) As Oklahoma gets closer to the 2019 tornado season, you can expect the predictions of what this year may bring to start piling up. But how accurate will any of those be? We sat down with National Weather Service-Tulsa Meteorologist-In-Charge Steve Piltz to find out what can be found from studying past seasons, and what (if anything) can be predicted for our upcoming season.

WHAT PREVIOUS YEARS HAVE SHOWN

The data over the last 70 years is known as the era of “modern” tornado reporting.

Let’s start with the big ones. Eight F5 or EF5s have hit statewide since the current era began, three of which have occurred in NWS-Tulsa territory. Most F5s or EF5s have occurred in NWS-Norman territory- like the notorious “Moore tornado” an EF5 that hit McClain and Cleveland Counties in 2013, killing 24 people. Or the F5 that hit Grady, McClain, Cleveland and Oklahoma Counties during an unprecedented outbreak in May 1999, which claimed the lives of 36 people.

Tulsa’s coverage area has not seen an F5 since one hit Choctaw and McCurtain Counties in 1982, one of three in our area since 1950. It was the only F5 Tornado to hit Oklahoma that whole decade. F5

Tornadoes, of course, have hit Oklahoma before the modern reporting era began. Like the Woodward Tornado in 1947 that claimed the lives of 116 Oklahomans. It was because of that tornado and others around the same time that the National Weather Service began their tornado watch and warning program in 1953.

In total, five F/EF 5s were recorded in Oklahoma before the “modern era” of recording began, bringing the statewide total of recorded F/EF 5s to 13. And no clear trend in sight.

Obviously, those monsters are the rarest. Regarding the number of overall tornadoes, the data indicates an increase here in NWS Tulsa’s County Warning Area, which covers 25 out of Oklahoma’s 77 counties plus 7 of Arkansas’.

The numbers are organized into decades. In our neck of the woods, there have been a steady amount of F-0 and F-1 tornadoes every ten years up until the 1990s, several every year. Those are the smaller ones, that don’t cause as much damage.

On the other end of the scale, the number of F-4 tornadoes appears to be between three and five per decade until the 2000s when it dropped to one during that ten year period. From then on, you see the number of tornadoes spike dramatically, with the number of F-0s quadrupling in the 1990’s, and staying high in the 2000’s.

A record number of EF-1s and tornadoes in general in the 2010’s must mean tornadoes are increasing every year, right? Not exactly.

“You see all of a sudden there’s a big change in the numbers in the 90s, 2000s, 2010s, that’s when you put more staff in the Tulsa weather office,” Piltz said. “So now there’s more people available to go look at things and you’re also putting staff in the office that was trained to do that kind of stuff.”

Piltz said Oklahoma records are not a consistent reporting system to try and pull trends from, given how rapidly scientific research has progressed over the years. Everything from how data is collected to the invention of social media has had an impact on the quality and frequency of tornado reporting and recording.

“We know how tornadoes tear up homes and so we can look at that and say yeah that home is tore up and it’s pretty bad but it failed because its garage door failed,” Piltz said. “Then you just began to have this cascading effect of damage that we know now can suggest it was not as strong a tornado as we thought. But say 50 years ago we would have said ‘oh my gosh’ that was a much stronger tornado.”

Meanwhile, Oklahoma engineers have had decades of their own advancements, building structures to better withstand the force of tornadoes.

“Maybe the tornadoes were the same exact strength but because of how they tore things up are different now, would get them a different rating,” Piltz said.

Flash forward to 2018, when Oklahoma saw the quietest start to a tornado season on record. Could that be the new trend? The only thing Oklahoma’s data can confirm is nothing stays quiet for long.

“Four years in a row that were very quiet tornado-wise and all of a sudden you’re back at the peak for several years and then you’ve got three or four years in a row that are quiet and then you’re back at a longer peak that ran for a while,” Piltz said. “So I think it would be dangerous to say that oh it’s been quiet for several years therefore we’re done.”

Piltz said while 70 years of “modern data” and the smattering of data before that may seem like a lot, it’s really not a large pool to pull from, especially when the numbers are all over the place.

“To basically say that we know all we think we need to know about tornadoes from 1950 forward is probably not wise,” Piltz said. “There are long trends and that is good but we know in the broader scheme of the world much longer history exists there and we have no real clue what happened in this neck of the woods prior to 1850 or thereabouts. Even just records of the initial folks in here are pretty spotty.”

UNDERSTANDING THE FORECASTING SYSTEM

So, what good is all this data anyway? For one thing, meteorologists have learned a great deal about how storms form, and what kinds of storms produce tornadoes. That helps them better protect the public.

Storm systems are tied to the oceans. The oceans and the atmosphere are tied together. Both are always changing, especially before they make it here to landlocked Oklahoma.

“We’re far enough away from the Atlantic and the Pacific that connections aren’t nearly as solid as you may think. So, for California, south Texas, across Florida, you can say things like hey this season really ought to lean a certain way because when we see those ocean connections start to happen it’s probably really going to feedback into the atmosphere over those areas,” Piltz said. “When we see that start to happen and we’re looking at it up here yeah there’s going to be some storminess around but it may be over south Oklahoma and north Texas it may not be as far north as Tulsa.”

Weather officials continually deal with forecasts that are accurate one day, and then completely different the next based on those oceanic and atmospheric changes. Radar might be able to indicate when storms are forming weeks in advance, but where they will end up is pure guesswork. And what kind of radar is available and where makes things that much trickier.

Out in the oceans, measurements are taken via satellite. Down in Mexico, they have less measurement equipment. Sometimes meteorologists in Tulsa don’t get good data to make predictions until the storm is just 12 hours away.

“Now in the five to ten day period we might look at it and say there’s going to be tornadoes in the plains,” Piltz said. “That could be Nebraska that could be central Texas, could be Oklahoma. So I think somewhere at a ten day period you could say yeah we need to watch out this system is going to tear something up between Omaha and San Antonio and then you let the predictions define after that.”

As for confident predictions for Tulsa, Piltz said due to the ever-changing elements, the only predictions you can really trust confidently are the ones that are made no more than five days out. Another thing to keep in mind is perspective. Meteorologists, emergency responders and the general public all have a different perspective as to what qualifies as an accurate forecast.

“If it’s the public if it’s not within 15-20 miles of them they might not think that they had a bad storm,” Piltz said. “But the emergency manager’s going to know, ‘man that was a close call.’ If it’s 50 miles away they might be going ‘I’m glad that thing missed us because that would have torn our town up.’ So everybody has their own zone where they’re going to score was that forecast a hit or not.”

FINAL THOUGHTS ON TORNADO SEASON 2019

Piltz said in the end, it’s important to remember there’s still a lot we don’t know about tornadoes.

“It really still only takes one storm system to come across the area at the right time to suddenly produce quite a few tornadoes and then when people ask is it going to be a bad tornado season and the only real answer to that is if there was one in your back yard it was a bad season,” Piltz said.

For information on tornado safety, visit https://www.weather.gov/safety/tornado

SPECIAL THANKS TO

Steve Piltz, National Weather Service-Tulsa

National Weather Service-Norman

National Severe Storms Laboratory/ National Oceanic and Atmospheric Administration