Weather 101: Understanding Oklahoma's severe storm, tornado threats

By Cindy McIntyreMay 26, 2016

Weather resource
Zac Scott, KSWO-7 meteorologist in Lawton, Okla., begins reporting the potential for severe weather several days out. During storms that could spawn tornadoes, large hail or floods, Scott and the SkyWarn weather team keep viewers continuously informe... (Photo Credit: U.S. Army) VIEW ORIGINAL

FORT SILL, Okla., May 26, 2016 -- Editor's note: This is the third in a series on tornado and severe weather preparedness.

Thunderstorms happen all over the world, but there's something in particular about the middle part of America that gives it the nickname Tornado Alley.

That "something" is the convergence of two major types of atmospheric conditions: warm, dry air from the west, and warm, humid air from the south. The meeting point of these two systems is called the dry line, a weather term most parts of the country don't use.

"The dry line is a very unique feature for Kansas, Oklahoma and Texas," said Zac Scott, meteorologist for Lawton's KSWO-TV Channel 7.

That convergence allows the moist air to rise high into the atmosphere, where it cools and forms precipitation. It is also a zone of instability that creates thunderstorms, particularly supercells which rotate due to wind shear and can form tornadoes.

"Wind shear is the turning or strengthening of winds as you go up in the air," said Austin Bowling, Channel 7's chief meteorologist. "The atmosphere is kind of like a cake. The lower level winds could be coming from the southeast at 15 to 20 miles per hour. As you head up higher into that cake at around 40,000 to 50,000 feet you've got winds coming straight out of the west at around 50 to 70 mph. Everything is turning as you're going up and everything's getting stronger."

Determining whether rotation seen on radar is a tornado can only be verified by a visual sighting, what they call "ground truth." That's why the Channel 7 meteorologists are storm chasers. But they are quick to point out even with their training, storm chasing is dangerous.

Bowling cited the multiple-vortex tornado in El Reno, Okla., May 31, 2013, that killed three chasers.

"We had extremely talented, extremely well-trained scientists trying to drop probes in front of it. The tornado moved in a direction they were not prepared for. They got caught off guard and they were killed."

That EF-3 tornado's path of destruction was 2.6 miles wide, making it the biggest known tornado.

Tornadoes can change speed and direction, and because of the popularity of storm chasing there are often traffic jams that prevent quick escape. The best advice is to listen to weather forecasts days in advance and check local conditions as severe weather approaches.

"Before you leave from work or home know what the weather is going to do," said Bowling.

Scott and Bowling say they give talks to area schools and to many units at Fort Sill about severe weather preparedness. As meteorologists they do their own forecasts, using computer models and predictions from the National Weather Service and the Storm Prediction Center, as well as their own evaluations of atmospheric conditions.

"I've spent four, four-and-a-half hours today (May 20) looking at each layer of the atmosphere to see if everything's coming together at the same time," said Scott.

"We break down each layer of the atmosphere to see if that moisture's there at the surface, if we can get the turning of the winds, if we can get that upper level of support that energy or lift to take that warm moist air at the surface and put it up with the cold air," he added.

They use their knowledge of what typically happens in Texoma, and conditions that might not be taken into account in a generalized forecast. Recent rains, for instance, can increase ground moisture, which can add to the moisture being drawn up into thunderheads.

When the severity ramps up, so does the weather team. Watching KSWO-TV during a severe weather threat gives an indication of all the sources of information coming into the station. These consist of social media posts of current conditions, alerts from the National Weather Service, Scott studying the radar, ham radio reports (many storm spotters use ham radio), Matthew DiPirro and Katie Western observing in the field, and Bowling in front of the camera with the weather visuals and tracking information.

Everyone should monitor real-time weather information, available through Channel 7 SkyWarn, NOAA, Weather Underground, and Intellicast, but don't rely on just one source.

Radar shows the direction of travel and certain components of a storm using colors. Blue indicates drizzle, green is rain, yellow-orange-red is heavier rain and often thunderstorms. Pink or lavender could indicate hail. Occasionally black is seen, which could indicate a debris ball from a tornado if it is in a certain portion of the supercell.

Watches and warnings are issued by the National Weather Service and the Storm Prediction Center. Channel 7 relays that information, and cell phone carriers often send a tone alert to their subscribers' smart phones. Weather radios can also be programmed to set off an alert tone for selected severe weather, even while one is asleep.

Bowling realizes people can often become complacent with all the severe weather watches and warnings that don't pan out, or miss forecasted areas.

"It only takes one really bad tornado for it to be one that is remembered by everybody," he said.

Because Lawton is a highly mobile community, newcomers may not have local knowledge that can help them deal with severe weather reports.

"Be familiar with what county you're in, what towns are close to you, with the highways, with some of the counties near you, the area you're in," said Bowling. "You're going to hear a lot of county names and town names (on the weather report)."

He said showing video from the field helps people see the storm's power and the need to take shelter.

"I can tell you where it is, where it's going or doing, but in the end it's your responsibility. You're the one who has to act and have a plan with your family."