Despite the fact that we’ve known about tornadoes for thousands of years and that meteorologists are actively studying them (and have been doing so for decades), there are still a lot of unknowns about these storms. We already know a fair amount about how twisters start, but many people wonder how does a tornado stop? It may seem like Mother Nature is turning a tap on and off, but there’s a lot more to it than that.
In this article, we’ll go over the causes that make a tornado stop and the science behind it. We’ll cover this starting with how tornadoes form, before getting to how they stop. Understanding the full cycle of a tornado is key to understanding how a tornado stops.
Understanding the Tornado Lifecycle
All tornadoes are thunderstorms but not all thunderstorms are tornadoes. Each twister starts life as a thunderstorm and some ways behave in the same way as a thunderstorm. Certainly, most people are familiar with the tell-tale signs of a thunderstorm emerging, but few understand what makes the thunderstorm stop.
The Thunderstorm Phase
Thunderstorms are made of clouds. Those clouds form in exactly the same way as any other. Warm air rises and cools, causing water vapor to condense together into the form of a cloud. This is a normal process of evaporation, but thunderstorms occur when the updraft of low-pressure air continues upwards, making the cloud taller.
Thunder clouds can reach 40,000 feet (12,192 meters) into the troposphere layer of Earth’s atmosphere. As more water is condensed, great forces of energy continue to heat up frozen water at the upper reaches of the cloud. As the updraft continues to heat, the kinetic energy becomes too much, and the cloud explodes into rain, lightning, and thunder.
When a thunder cloud eventually releases, it produces massive amounts of energy. In fact, 10 million kilowatt-hours of energy, or around the same as a massive 20-kiloton nuclear bomb.
The Tornado Phase
Tornadoes don’t magically appear. You will not see a twister without a thunderstorm. Tornadoes are born in supercell thunderstorms, which have stronger upward air updrafts than regular storms. When this updraft is strong enough, a vortex of water is formed, resulting in what’s called a mesocyclone.
Once this happens, there is a 50% chance a tornado will also form within a half-hour. If a twister does happen, it moves downwards through the thunderstorm cloud as a swirling vortex of powerful air. Wind speeds generated by the storm reach anywhere from 120 to 300 mph (up to 483 kph). It is worth noting the vortex only becomes a tornado when it touches ground, which does not always happen.
When it does, we are very familiar with the visual and physical results. Tornadoes are perhaps the most recognizable weather event in the world.
On the ground, it’s easy to assume the twister has a mind of its own and is seemingly choosing targets. That’s not the case because the tornado is linked directly to the thunderstorm. This means its path is entirely dictated by the route of the thundercloud that generates it.
How long the tornado lasts also depends on the thundercloud. Some last mere minutes and move less than a mile. Bigger twisters can run for hours, covering dozens of miles, and cause massive damage along the way.
The Ending Phase
So, how does a tornado stop? As you may have realized, nothing about the formation, movement, and lifespan of a tornado is without reason. It’s all related to thunderstorms. That also seems to be the case when a tornado dissipates.
The science on what causes tornadoes to stop is still relatively new. There is plenty of debate around the exact reason why a storm will die. Many believe the thunderstorm plays a direct role in the collapse of the spinning mesocyclone.
Importantly, the thunderstorm itself may continue long after a tornado born from it dissipates. However, changes within the storm can remove the prime conditions a twister needs to form. If moisture levels are wrong or the airflow is broken, the tornado will stop.
Why Do Twisters Sometimes Come Back?
Movies would have us believe that tornadoes can dissipate and then return seemingly with intelligence, targeting people and houses like they have a vendetta.
Mother Nature is clever, but she’s not that good! Skipping twisters are something of a tornado myth, but that does not mean a tornado cannot dissipate and return.
In fact, it’s common for a tornado to briefly disappear before returning. As previously noted, the path a twister takes is entirely dependent on the storm cloud that generates it. When the vortex is disturbed the tornado can dissipate, sometimes never to come back. However, occasionally the disruption in the vortex is temporary.
When the vortex repairs itself, it can touch ground again and cause the tornado to come back. For some, this looks like the tornado is hopping or skipping but that’s not really what it is doing in a literal sense.
There is some debate because it is a worthy question to ask whether multiple touchdowns from the same thunderstorm is the same tornado or different twisters. If they were different tornadoes, the idea of a skipping storm may be more likely. If it is just the same twister coming and going, it is not really skipping.
When we look at the idea of skipping tornadoes, there are a few possibilities:
- A single thunderstorm produces multiple tornadoes that dissipate and generate from the same vortex.
- Continuous tornado that seemed to disappear because the contact with the ground was relatively weak.
- One tornado that keeps generating and dissipating, landing in different locations and seemingly hopping.