The area stretching from Texas to Minnesota has the greatest known occurrences of severe thunderstorms in the U.S. according to the "Weather Spotter's Field Guide" written by staff members at the National Oceanic and Atmospheric Administration. No place in the U.S. is immune from the forces of these storms.
At a storm spotter class held on Fort Riley March 22, Chad Omitt, warning coordination meteorologist, National Weather Service, spoke about different types of thunderstorms focusing on supercell storms.
"A vast majority of what we talked about are what we call supercell thunderstorms that rotate," he said. "They have rotating updrafts. A vast majority produce hail, high winds and if the conditions are right, they can produce tornadoes. Even if they don't produce tornadoes, the lightning, the heavy rain, potential flooding and the hail are all hazards. We want people to have an awareness of what thunderstorm hazards are and how to reduce their vulnerability to those hazards."
Lightning is an underrated killer, according to the guide. Nearly as many people lose their lives to lightning strikes as they do tornadoes, but because it typically hits one or two people at a time, fatalities receive less publicity.
Lightning is the "visible channel of light you see," Omitt said.
"We always just assumed it started at the cloud level and traveled down," he said. "It doesn't always happen that way. There is some times you get a channel that begins at the ground and maybe connects midway through the channel that develops out of the ground. It happens in a number of ways, but it happens so fast that you're not going to see it if it's so close that it will be a threat to you."
Omitt stresses safety during thunderstorms.
"I always talk about safety -- if you're close enough to hear thunder, you're close enough to be hit by lightning," he said. "No matter how it forms or what it looks like -- it's dangerous."
Thunder is the sound of the channel of air expanding formed by lightning.
The general guideline for judging distance from a lightning strike is count the seconds from the time the flash of the lightning occurs until the thunder arrives, then divide by five.
"That gives you a rough idea of how far away in miles the lightning is," Omitt said. "The take away is this, if you're close enough to hear thunder, you need to go inside and reduce your vulnerability from lightning that way. If you can, get inside, get into a hard-top vehicle roll up the windows and keep your hands inside. That's the fastest way to keep yourself safe."
The temperature in the atmosphere along with other variables, Omitt said, can change the equation. So, again Omitt stressed getting inside some shelter to remain safe during storms.
A severe thunderstorm has at least one of the following according to the guide; hail that is one inch or larger -- the size of a quarter, wind gusts of at least 58 mph or a tornado.
Heavy rains are generally associated with severe thunderstorms and bring the potential for flash flooding.
"Usually around here in Kansas, flash flooding is going to be from a thunderstorm," Omitt said. "A tense, heavy, shorter duration -- maybe an hour, two or three -- of rainfall that causes runoff and water flowing over roads and things like that. Or crossings where you might get caught in water that is deep enough to make your car buoyant and there's a current. That's a terrible situation and that's how most fatalities happen."
Most fatalities, Omitt said, occur when people are driving at night and they do not realize the water level is as high as it is and they get swept away.
"We just tell people that if you come to a flooded road, as best you can, turn around, don't drown," he said referring to the NWS slogan. "That's what we want people to do, we just don't want people risking themselves because it is dangerous."
The amount of rain needed to cause this flooding varies depending on the conditions of the soil he said.
"We have what we call flash flood guidance," he said. "There is some science to it of how much rain a certain area can absorb before it starts to cause runoff and flooding. And just based on the time of year and the soil conditions, that will vary quite a bit. This time of the year, because of our conditions being saturated, we can't take much. But sometimes, if we're real dry, in May or June when the crops are growing, there are spots that can take three or four inches and not have a huge impact. Whereas if that would happen today -- anywhere -- we would have serious impacts in terms of water and flooding."
Heavy snows and rain in Nebraska have caused major flooding in the state recently with 75 percent of the 93 counties declared emergency zones due to the high water. This water moves south toward the Gulf of Mexico through rivers, which has caused flooding issues in other states.
"As the soil conditions change and become wetter, they become saturated, they can't absorb any more moisture," Omitt said.
"It just doesn't take that much rain to cause runoff and flooding. So, we hope to get some dry weather so we can dry out, because our soils are awfully wet, awfully saturated."
The guide listed several safety tips for flooding:
• Turn Around Don't Drown. Do not attempt to drive or walk across a flooded road or low water crossing. You cannot be sure about the depth of the water or the condition of the roadway. The road might be washed out.
• Two feet of moving water will carry away most vehicles
• Six inches of fast-moving water can knock people off their feet
• If a vehicle is suddenly caught in rising water, leave it immediately and get to higher ground
• Be especially vigilant at night when flash floods are harder to recognize.
The weather pattern has been active over the last few months, Omitt said. With this, if the patter continues this way spring will include more storms.
"You look at the pattern that we are in and the pattern that we've been in for the last few months it is an active pattern," he said. "We've got frequent storms moving in off the Pacific, through the west coast, into the Rockies and eventually into the Great Plains. Now, as we get into March and April, we're still in the pattern but those storms are gradually moving farther to the north.
"As the storm track moves further to the north, at some point we're going to find ourselves on the south side of the storm track," he said. "By that I mean, we're going to be on the warm side. Where we've got the moisture from the Gulf of Mexico and areas where you can get thunderstorms. If this pattern persists through April and May then we could have more frequent opportunities for storms -- and maybe severe storms."
Chris Hallenbeck, emergency management coordinator, Directorate of Plans, Training, Mobilization and Security, reminds everyone of the Ready Army mantra -- Be Informed, Make A Plan, Build A Kit and Get Involved.
"Remember that preparedness is everyone's responsibility," he said.