Tornado in a bottle

In this activity, students will observe the formation of a water vortex by swirling water from one bottle into another. The vortex allows the water to drain smoothly and rapidly while air flows upward through the center, similar to the dynamics in a real tornado.

Transcript

In this video, we'll create a tornado inside a bottle using only a few materials. For this demonstration, you will need two empty bottles, water, and a plastic tube connector. If you don't have a connector, you can create one yourself by using a washer and duct tape. In addition, you can add food coloring to the water, and if you want to prevent any leaks, you can use plumbers tape. Now, let's start our activity by filling one bottle about 2/3 full. Add about two to three droplets of food coloring and mix well. Let's attach the connector tube to the filled bottle. Once that's secured, screw the empty bottle on top. Make sure both sides are tight to prevent any leaks. Next, flip the setup so the full bottle is on top. Hold the top bottle and gently swirl it in a circular motion. You'll start to see a vortex form. And just like that we've made a tornado inside a bottle. When starting this activity, you might think that the bottom bottle is empty but it's actually full of air. When we flip the setup without swirling, the water drains very slowly. That's because the air in the lower bottle can only rise in bubbles, and that holds the water back. But when we swirl the top bottle, we create a vortex. The spinning motion forms a central hole due to centripetal forces. This hole allows air from the bottom to rise smoothly through the center while the water drains through the sides. In the real world tornadoes don't form from water, but from rapidly rotating air. But this is a simple activity to understand how air flows through the center of a tornado's funnel. Thanks for watching this video. For more activities and resources like this, visit the NOAA Office of Education website.

Grade range: K – 12
Setting: Classroom, outreach events, or at-home activity
Estimated time: 10-15 minutes

🌪️Background: What is a tornado?

Tornadoes are rapidly rotating columns of air that form underneath certain types of thunderstorms. They create a visible funnel that can stretch from the base of a storm cloud to the ground, picking up debris, water droplets, and dust.

Tornadoes form when specific atmospheric conditions come together:

Instability: Warm, moist, less dense air near the ground with cooler, dry, denser air above. This unstable configuration causes the lighter air to rise rapidly, disrupting the atmosphere’s balance.
Wind shear: A change in wind speed or direction with height, which causes rotation.

Updrafts (rising air) in unstable conditions, combined with wind shear, can tilt and stretch this rotation, potentially forming a tornado. Tornadoes can cause fatalities and injuries, as well as significant damage to property each year. Forecasts and tornado warnings are issued by the National Weather Service and are fundamental in protecting life and property.

Learn more about tornados with our resources below!

🧪Materials

Two empty plastic soda bottles (1- or 2-liter)
Tornado tube plastic connector
Water
Food coloring (optional, improves vortex visibility)
Plumber’s tape (optional, for preventing leaks)
Glitter (optional, simulate debris)

🧭Instructions

Fill one bottle about two-thirds full with water.
Add a few drops of food coloring and/or glitter to better visualize the vortex (optional).
Attach the tornado tube securely to the filled bottle.
Connect the empty bottle to the other end of the tornado tube.
Flip the bottles so that the bottle with water is on top.
Swirl the top bottle in a circular motion to create a vortex. Do not shake!
Optional: If water leaks from the connector, unscrew the bottles and apply plumber’s tape around the threads of the connector, then reconnect.

💡What is happening?

When the water bottle is inverted without swirling, water drains slowly because air must bubble up through the falling water.
The pressure difference between the two bottles and the surface tension of the water can hold back the water flow or stop it completely.
When you rotate the bottles in a swirling motion, the water in the upper bottle rotates as well. This creates a vortex, a spinning motion that forms a central hole due to centripetal forces.
This central hole allows air from the bottom bottle to rise smoothly into the top bottle, while water drains more quickly into the bottom bottle.
This mimics how air flows through the center of a tornado’s funnel.

🔍Scientific connection

Real tornadoes don’t form from water, but from rapidly rotating air. This demonstration helps visualize how spinning motion and vertical airflow interact in a storm system:

Upper bottle: Represents storm clouds full of moisture.
Water movement: Mimics the downward motion of rain or a funnel cloud.
Air bubbles (updrafts): Rising warm air in thunderstorms.
Swirling motion: Analogous to the rotational force caused by wind shear in real storms.

⚠️ Safety notes

Make sure the tube connector is securely fastened before flipping bottles.
Supervise younger children during assembly and swirling.