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# Stormy: What is the Eye of a Hurricane?

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Source:
Author: Janice VanCleave

### Problem

What is the eye of a hurricane?

### Materials

• 2-quart (2-liter) plastic bowl
• Tap water
• Scissors
• String
• Ruler (the kind that has been punched for a three-ring binder)
• Paper clip
• Black pepper
• Wooden spoon with a long handle

### Procedure

1. Fill the plastic bowl three-fourths full with water.
2. Cut the string so that it is 1 inch (2.5 cm) longer than the height of the plastic bowl.
3. Tie one end of the string to the paper clip.
4. Thread about 1 inch (2.5 cm) of the free end of the string through the hole in the center of the ruler. Tape the end to the ruler.
5. Sprinkle pepper over the surface of the water in the bowl.
6. Stir the water with the spoon in a counterclockwise direction a few times.
7. While the water is swirling, quickly suspend the paper clip in the center of the swirling water. Try to drop the paper clip directly in the center of the spiral made by the swirling pepper specks.

### Results

As long as the paper clip remains in the exact center of the swirling water, it moves slightly or not at all.

### Why?

The swirling water in the experiment represents a hurricane. A hurricane is a large tropical storm with winds of 74 miles (118 km) per hour or more that rotate around a relatively calm center. The center of the swirling water in this experiment simulates the calm area in the center of a hurricane called the eye of a hurricane. The eye is a long, vertical tube of relatively motionless air in the middle of the storm. The distance across the eye of a hurricane varies depending on the size of the storm, but it averages about 20 miles (32 km) across. This area of calm air reaches all the way to the Earth's surface and has high-speed winds spinning around it. In the Northern Hemisphere a hurricane's winds spin counterclockwise around the eye, and in the Southern Hemisphere the winds spin clockwise. Like the air in a hurricane's eye, the area in the center of the swirling water in the bowl is relatively calm, as is indicated by the paper clip's lack of motion.

### Let's Explore

1. How would suspending the paper clip near the side of the bowl affect the results? Repeat the experiment twice, first suspending the paper clip in the water on the side nearest to you, and then suspending the paper clip in the water on the side farthest from you. Science Fair Hint: Use the results of this experiment to illustrate how the direction of the winds of a hurricane would change as it passed directly over you. Find out more about the weather conditions you would experience during a hurricane. A diagram illustrating the results can be used as part of a project display.
2. Does the size of the container affect the results? Repeat the experiment twice, first using a smaller bowl, and then using a larger bowl. Science Fair Hint: Find out more about the size of hurricane eyes. Does the size of the eye increase as the storm increases? Does the rotation speed of the storm affect the size of the hurricane's eye? Display drawings of hurricanes, comparing their size to the size of their eyes.
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