Published: April 9, 2020
Facing a tornado and flash flooding can be terrifying, and when you put the two potentially deadly threats together, it can be paralyzing.
Where do you go? Do you climb to your roof or into the basement, and which threat takes priority?
This is an increasingly problematic and common scenario in some parts of the country, and the answer is not easy.
The Bottom Line:
The simple answer is to go into your interior-most room on the lowest floor of your house as you would in a tornado warning, but this is not always the best answer.
So what do you do if you live in hypothetical Town B, shown below, if you're being faced with both a tornado and a flash flood warning?
As long as flooding is not an imminent threat, as in water is already quickly approaching or coming into your house, you should move to the most interior room of the lowest level of your home or building.
If flooding is ongoing, you should go to the most interior room of the lowest dry level in your home.
As always, never stay in a mobile home if severe weather is headed in your direction.
Make sure to make this decision as quickly as possible after a warning is issued because time is usually running out. Your decision may be different from your neighbor's decision, but both may be correct depending on your situation.
A hypothetical situation where a tornado warning and a flash flood warning are issued at the same time for the same location.
Is this really the best solution?
Well, we asked around the National Weather Service to see if there was an official direction in this situation. The responses that we received were somewhat scatter-brained, but centered on trying to evaluate your own situation to see what the best thing is for you to do.
One of these responses was from Rick Smith, the Warning Coordination Meteorologist at the National Weather Service office in Norman, Oklahoma: "If it were me, I would have to weigh which threat poses the most danger to me at that moment and react to that. And each person's individual circumstances at that moment will determine what they should do."
Warnings are issued for both flash floods and tornadoes, but these two warnings, when in effect for the same location at the same time, offer contradictory advice.
Take for instance the following "Call to Action" statements that are often found in warnings across the country:
Tornado Warning (This is what you should do in "Town A" above):
TAKE COVER NOW! Move to a basement or an interior room on the lowest floor of a sturdy building. Avoid windows. If you are outdoors, in a mobile home, or in a vehicle, move to the closest substantial shelter and protect yourself from flying debris.
Flash Flood Warning (This is what you should do in "Town C" above):
If you are in the warned area move to higher ground immediately. Residents living along streams and creeks should take immediate precautions to protect life and property.
This situation is not a rare conundrum.
Research done at Colorado State University "reveals that every year about 400 tornado and flash-flood warnings are issued within 30 minutes of each other for the same area, which was more frequent than expected," according to a paper released in Physics Today in 2016. Sixty-eight of those tornado/flash flood combination events (TORFF) were confirmed between 2008 and 2013, according to Lance Wood, Science Operations Officer at NWS Houston.
This problem is increasingly common and can occur a number of ways, two of which are discussed below:
Severe Weather Event
Multiple TORFF situations arose on May 31, 2013, in central Oklahoma as severe, tornadic supercells bombarded the Oklahoma City metro area.
One of the tornadoes that night was a very large EF3 tornado that struck the town of El Reno, Oklahoma, near Oklahoma City, as a part of a slow-moving weather system that also brought severe flooding to the region. This tornado was only one of 12 tornadoes that struck central Oklahoma that night. Up to 8 inches of rain also fell as these severe thunderstorms rode over the same locations again and again.
The El Reno Tornado
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The service assessment from this event completed by the NWS found that people were sufficiently warned about the tornado, but "no members of the public interviewed were aware of a flash flood warning on May 31." This was likely due to the focus on the tornadoes that evening.
"In fact, those interviewed indicated the flash flooding was a surprise and they did not know how to respond to the dual warning," according to the assessment. "They knew what to do for a tornado or for a flash flood, but not for both at the same time. The surprise element of the flash flooding made the public feel less confident about its safety plans."
In all, 14 people died in flash flooding and eight people died in the El Reno tornado itself. The flooding was Oklahoma's deadliest flood incident in nearly 30 years.
Tropical Situation
This exact situation became common during Hurricane Harvey, which brought both biblical flooding and a high number of tornadoes to eastern Texas and western Louisiana in 2017.
Some emergency messages released by the Emergency Managers in Houston even told people to "get on the roof" due to rising flood waters.
Yet, tornado warnings were being issued in the days leading up to and following the landfall of Hurricane Harvey, and each one of those warnings said "move to the lowest floor of a sturdy building."
Both widespread flooding and tornadoes continued for days as Harvey slogged through the upper Texas coast.
It is unknown exactly how many people Harvey killed by flooding and tornadoes, but at least 68 people were killed directly by the hurricane overall.
Warnings Are Beginning to Change
This conundrum is an evolving discussion within the National Weather Service, but the way tornado and flash flood warnings are being constructed are starting to get smarter. Soon, you'll no longer see a statement telling you to get down into flood waters when a tornado is on its way.
Frank Alsheimer, Science and Operations Officer at the NWS Office in Columbia, South Carolina, added that in practice, their office has an option that "removes the suggested action of finding a low ditch and recommends moving inside a sturdy building that’s not in a flood-prone area" if a tornado warning and flash flood warning are going to be in effect at the same time.
Jeff Evans says that the Houston/Galveston office is "hoping to get our warning program set so we can tweak the call to action statements to highlight the most significant of the two threats."
When severe weather happens, always remember to stay tuned to your local weather service office and right here at weather.com for the latest.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
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